1046 Saint Genevieve (Abancay) - Salt River

display this bandwidth, notably Moonbi and Saint Gen­evieve County. Of these two, Saint Genevieve is structurally so closely related to Abancay that it is impossible to find any differences at all. The analytical data for the two irons, for both major and trace elements, agree surprisingly well. The hardnesses of all phases are identical. The state of corrosion is identical. The Abancay specimen I studied , Tempe No. 209.ax, is even cut through the parent taenite crystal in exactly the same direction as several Saint Genevieve specimens also examined by the author, a fact which is a surprising coincidence.

Having noted these facts, I asked for Dr. Nininger's advice. In a letter of February 20, 1970, he answered:

"The specimen, so labelled , lay in the Ward Natural History Establishment on occasion of several of my visits, but no one could give any further information. Finally in one of our exchanges I received it hoping to be able to find some information, but never did. If your surmise is correct then somebody must have made a wild mistake somewhere. After their big fire some problems of labeling plagued them ... ".

It appears to me that the evidence for Abancay being an individual, separate meteorite is very meager indeed. The fragmentary nature and the fact that the specimen original­ly came from Ward's, who at various occasions cut Saint Genevieve material, indicate strongly that Abancay is a mislaid Saint Genevieve specimen. Perhaps the name Aban­cay was originally attached to some mineral specimen, which after the fire (September 30, 1930) was interchanged with the meteorite slice. Tambo Quemado is the only other recorded meteorite from Peru and this is defmitely differ­ent from Saint Genevieve (Abancay).

Salina , Utah, U.S.A.

38°59'N, 111°51'W

A number of shale-balls, up to 2 kg in weight, were found about 1908 around a small depression in the Pahvant Mountains, 15 miles

Figure 1490. Salina (U.S.N.M. no. 1272). This meteorite is con­verted to limonite, except for some minute patches, only visible under the microscope. Scale bar 10 mm. (Perry 1944: plate 77.)

from Salina, Sevier County . Only one completely weathered fragment of 235 g has been preserved. It was described by Perry (1939c; 1944 : plate 77), who cautiously concluded that the mater­ial was originally a medium octahedrite. Buddhue (1957 : 121) briefly discussed the material.

Specimen in the U.S. National Museum in Washington:

221 g fragment (no. 1272,6 x 4 x 4 em). The only known sample .

Salta. See lmilac (in the Supplement)

Salt River, Kentucky, U.S.A.

Approximately 38°01N, 85° 45'W; 150m

Plessitic octahedrite, Opl. Spindle-width 70±20 J.L. Artificial a 2 •

HV 178±8.

Group IIC. 9.80% Ni, 0.5 7% Co, 0.43% P, 39 ppm Ga, 99 ppm Ge, 6.6 ppm Jr.

As discussed in the following entry, Tocavita also belongs here. All specimens have been artificially reheated to about 1000 or 1050° C.

HISTORY

A mass of unknown weight was found by J. Watters near Salt River , a tributary of the Ohio , about 20 miles south of Louisville. The mass was "heated in a forge by its original proprietor, to remove a portion, and, in this process, the original form was somewhat defaced" (Silliman 1850). When the main mass reached Silliman, it weighed 3.6 kg, but material from the same mass was still said to be in private possession. The total weight-may have been about 4 kg, estimating from the early descriptions and from what is preserved in collections. Silliman described and analyzed the material , and Rose (1864a: 70) examined the specimen in Berlin. Reichenbach (1859: 175 ; 1862b: 578) discussed the iron at several occasions. Cohen (1900a: 74; 1905: 275) presented a new analysis and, in his description , compared Salt River to Tocavita and Ballinoo. Brezina & Cohen (1886-1906: plate 30) gave three photomicrographs and again emphasized the remarkable resemblance to Tocavita. Also Buchwald & Wasson (1968: 23) noted this similarity and expressed the opinion that Tocavita might be mis­labeled Salt River material. They presented two photo­micrographs (Figures 15 and 16) to show how the artificial reheating had altered the material.

COLLECTIONS

Yale (751 g), London (492 g), Harvard (272 g), Am­herst (I 48 g), Washington (I 11 g), Chicago (79 g), Tiibingen (61 g), New York (60 g), Calcutta (48 g), Vienna ( 45 g), Paris (34 g), Tempe (34 g), Stockholm (27 g), Dresden (20 g), Berlin (19 g), Ottawa (17 g), Gottingen ( 13 g), Vatican (11 g), Strasbourg (7 g). Of "Tocavita:" Tiibingen (No. 2220 of about 300 g; No. 2294 of 22 g), Chicago (No. 1155 of 15 g).

DESCRIPTION

From the original reports and from the sections preserved the mass may be estimated to have measured 12 x 10 x 8 em . The largest specimen extant, in Yale, is a 751 g block averaging 5 .5 x 4.5 x 3.5 em in size. The original surface on this and other specimens is corroded and covered with 0.1 -1 mm thick crusts of oxides. Locally, pockets of rust, 5-6 mm deep, are present. The crust shows unambigu­ous signs of reheating, corroborating the original report by Silliman (1850) who stated that the mass had been artificially reheated. Salt River is an important documented sample showing what one may expect to find when an iron meteorite has passed a smithy.

No fusion crust and no heat-affected zones are present; presumably they had been removed by corrosion before the mass was found . Etched sections display a plessitic matrix in which a large number of spindle-shaped kamacite bodies are scattered. These are typically 70±20 J1 in width and 10-15 times as long as they are wide . The kamacite felt forms a Widmanstatten pattern on a microscale , but continuous lamellae are never present. Because of the

Figu re 1491. Salt River (Tempe no. 258a). Plessitic octahedrite of group IIC. Artificially reheated to about 1000° C so that the phosphides fused and the kamacite transformed to unequilibrated a 2 • Etched . Scale bar 400 J..L.

Salt River 104 7

artificial reheating all kamacite is transformed to serrated a 2 grains, 25 -50 J1 across, and with a hardness of 178±8 .

Plessite covers 25-60% of the surface, averaging about 50%. In the corroded rim zone , where the kamacite is selectively corroded, the original structu re is rather well preserved. It consisted of a regu lar, duplex a + 'Y mixture with easily resolvable -y-ribbons, 1-2 J1 wide. The artificial reheating made significant diffusion possible in the interior where it has blurred the plessitic matrix . The hardness is 220±15 .

Schreibersite is extremely common. It occurs as lamel­lae, only 50-200 J1 wide , but up to 10 x 5 mm in length . It also occurs as nodules, 20-100 J1 across and numbering 10-12 per mm2 • All the phosphides are micromelted - not just those near the surface . They have resolidified to beautiful, fme -grained eutectics with a hardness of 690±40. Spherical shrinkage cavities, 10-100 J1 across, are very common.

Troilite was observed only as a 20 x 16 mm nodule on one of the roughly cut surfaces on the Yale specimen. Graphite was reported by Silliman (185 0) and Reichenbach ( 1862b ), but this could not be supported .

Figure 1492. Salt River (Tempe no. 258a). Artificially altered. To the right, a fused schreibersite crystal within a kamacite lamella, now a 2 • In center, blurred diffuse plessitic mat rix. Etched . Scale bar 100 J..L.

SALT RIVER - SELECTED CHEMICAL ANALYSES

Sj ostrom in Cohen (1 898a: 140) analyzed Tocavita Tocavita (Chicago No. 1155); see Buchwald & Wasson material from Tubingen. Fahrenhorst in Cohen (1900a : 76) (1968 : 17, etc.). Since it is concluded below that Tocavita reported, among other things , 0.34% P. Smales' analysis is is mislaid Salt River material, the analyses quoted may be on authentic Salt River material. Wasson's first analysis is averaged to give the true chemical composition of Salt on authentic Salt River material , his second , on allegedly River.

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Sjostrom in Cohen 1898a 9.77 0.57 0.52 300

Smales et a!. 1967 14 106 234 0.9 40.1 99 Wasson 1969 10.02 37.8 100 6.3 Wasson 1969 9.63 38.7 96.1 6.8 Crocket 1972 8.4 17

1048 Salt River - Salt River (Tocavita)

The terrestrial, limonitic corrosion products have re­acted with the phosphides and created peculiar mixtures. A high temperature intercrystalline oxidation attack follows the austenite grain boundaries, forming a network with 20-50 J1 masks near the surface. Schreibersite melts have sweated out and mingled with the oxides that locally form intricate laceworks.

The description indicates that the iron was thoroughly heated to 1000-1050° C for, say, half an hour. What remains of the structure shows, however, that Salt River is closely related to Ballinoo and Kumerina, and , chemically , it forms a natural member of group liD (Wasson 1969).

There is hardly need for detailed description of the Tocavita specimens. It would be a word for word repe tition .

Specimens in the U.S. National Museum in Washington:

26 g par t slice (n o. 1131,6 .5 x 1.6 x 0.3 em) 25 g part slice (no. 1131 , 2.9 x 2.7 x 0.3 em) 60 g part slice (no. 2562, 3.5 x 3.1 x 0.7 em)

Salt River (Tocavita)

Plessitic octahedri te, Opl. Spindle-width 70±20 J.l . Artificial a 2 •

HV 180±10.

G roup IIC. An alysis : see Salt River.

HISTORY

During the examination of numerous Santa Rosa specimens (Buchwald & Wasson 1968), we encountered an unusually large number of mislabeled slices and fragments of various compositions and structures. Among these were three fragments labeled not only Santa Rosa but also with the synonym Tocavita and representing a rare meteoritic type that is similar to Ballinoo and Salt River. One was from the Chicago Collection (No. 1155) and two, from the Tiibingen Collection (Nos. 2220 and 2294). The latter had already been examined by Cohen (1898a: 139) who studied

Figure 1493. Salt River. The Tocavita sample (Chicago no. 1155). Plessitic octahedrite of group II C. Artificially alte red by reheating to about 1000° C. Etched. Scale bar 400 J.l.

Figure 1494. Salt River. Tocavita (Chicago no. 1155). all schreibers­ite crystals are fused , the kamacite is transformed to unequilibrated a 2 , and the plessite fields appear blurred due to imperfect homogenizing during the artificial reheating. Etched. Scale bar 200 J.l .

all the so-called Santa Rosa specimens in Reichenbacl} 's Collection. Cohen, and Brezina & Cohen (1886-1906 : plate 30), who presented two photomacrographs, correctly concluded that the two specimens represented material which was different from the bulk of Santa Rosa specimens and which resembled Salt River. We came to a similar conclusion and hesitatingly accepted that the three speci­mens represented authentic material from a meteorite that had been found on the hill of Tocavita east of Santa Rosa in Colombia. However, it was pointed out that they were extremely similar to Salt River specimens and might be mislabeled.

During the present study I have had an opportunity to see many more Salt River specimens; however, I have not been able to locate more Tocavita material , and I have come to the conclusion that Tocavita is not an independent meteorite but is mislaid material of Salt River. The reasons for this conclusion are given below. While one reason alone is insufficient, I believe that the combined points bring home the case.

I. Macro- and microstructures are identical . 2. The hardnesses are identical. 3. The analyses for main and trace elements give identical

results , within experimental error. 1

4. During terrestrial exposure both types of material have reached the same state of corrosion.

5. Both types of material have been artificially reheated to 1000-1050° C and have been slightly hammered.

6. While Salt River is a well documented mass found in 1850, Tocavita first emerges with Cohen's description (1898a: 139).

7 . Cohen examined two specimens from the late von Reichenbach Collection in Tiibingen. However , Reich­enbach himself never did mention the acquisition of any "Tocavita" meteorite, and he never discussed it in his various papers which were written between 1856 and 1865.

8. While in Santa Rosa Ward (1907: 3) inquired about Tocavita material but he neither found any fragments there nor in Bogota later. Nor were there any records or traditions in the community about a find separate from Santa Rosa.

9. About the year I900 the total amount of Tocavita material known was 338 g and 22 g - now 300 g, 22 g and 15 g. The large specimen is an endpiece, 8 x 5.5 x I em; the others are small sections. All may have been easily detached from the Salt River mass which weighed 3 .6 kg when Silliman received it.

IO. No record accompanied by a decent descripti.on and/ or analysis, was ever entered announcing the discovery of a Tocavita individual. I have shown previously that the ancient reports on Santa Rosa-Rasgata specimens are hopelessly confused and certainly cannot refer to Tocavita type material although the word ''Tocavita" is frequently used as a synonym for Santa Rosa.

II. Reichenbach (1859 : I75 and I76) had Salt River in his collection. And he had Santa Rosa/Tocavita material, labeled Rasgata, included under the same classification. A possible explanation for the later mix-up appears to lie here - with similarly (but wrongly) classified meteorites lying in the same drawer (?) and very difficult to tell apart with the naked eye. The mislabel­ing may have occurred after Reichenbach's death, when his collection was transferred from his castle on the Danube in Austria to Tubingen University.

Samelia, Rajasthan, India

25°40'N, 74°52'E

Medium octahedrite, Om. Bandwidth 1.10±0.15 mm. e-structure. HV 300±25.

Group IliA. 8.03% Ni, 0.49% Co, about 0.15% P, 20 ppm Ga, 3.5 ppm Jr.

HISTORY

Three masses were observed to fall in the Bhilwara district on May 20, I92I, at about 5:30pm.Onemass,of II25 g, fell in the Samelia jungle (25° 40', 74° 52'); another, of 587 g, in the Beshki jungle (25°39', 74°53'); and a third , of 750 g, in the village of Beskalai (25°39', 74° 47'). All masses were recovered quickly and donated to the Geological Survey of India, where Fermor (1924) gave descriptions and photographs of the exteriors and, in 193I, added some information about the structure with two photomacrographs of etched slices. Curatorial information has recently been given by Murthy et a!. (1969). Unfortu­nately, all previous descriptions and catalogs (e.g., Hey

Salt River - Samelia I049

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--..,r:. ,~~ A.-_ _· ~ ~:\ . ., _~·- ; .. ~ ' ? ::~tt-1' J • \

r - 0

(] ~ ~ :;;ig· :~ · ') ';._ ~ . ' .. ~:~ . ( - - . ' ~ ' - '

Figure 1495. Samelia (Brit. Mus. no. 1927, 916). Medium octahe­drite of group IliA. Fusion crust and heat-affected a 2 zone. The fusion crust has a magnetite layer (M), a magnetite-wi.istite layer ry-1) and several metallic dendritic layers, with gasholes. Etched. Scale bar 40 IJ.

I966: 423) have classified Samelia as a coarse octahedrite, which is incorrect.

The following is an extract from the eye witness reports in Fermor (1924).

The fireball moved from south to north and left a white trail in the sky. At the end of the trail the fireball burst thundering like a volley of guns, and several pieces dropped down to the earth. The 750 g mass penetrated the soil to a depth of 17 em, but no information is available as to the circumstances of impact for the other masses. The heaviest mass was reportedly found at the most northerly locality as would be expected if the flight were from south to north. The white trail in the sky disappeared after a quarter of an hour.

COLLECTIONS

Calcutta (the I ,I25 g and 587 g masses, undivided; 534 g, as sections through the 750 g mass), London (138 g), Minsk (7I g ?), Tempe (15 g).

DESCRIPTION

The three recovered fragments show a large range in sculpturing effects from the atmospheric flight. The 587 g mass, which measures 8.3 x 5 x 4 em, is rather well rounded, and original cleavage planes and fracture surfaces were smoothed in flight and were covered by fusion crusts of varying thicknesses.

The I , I25 g mass represents the opposite extreme. It is of a very irregular shape, measuring approximately II x 9 x 4 em, and shows protruding knobs and horns. The interest­ing fact is that the external shape is conditioned by the Widmanstiitten structure of the interior. Nearly all exterior

SAMELlA - SELECTED CHEMICAL ANALYSES

percentage Reference Ni Co P c s Cr

Cobb I967 8.03 0.49

Cu

I75

ppm Zn Ga

20

Ge Ir Pt

3.5

1050 Samelia

Figure 1496. Samelia (Brit. Mus. no. 1927, 916). The heat-affected a 2 zone has during its rapid progress temporarily been stopped by a preexisting grain boundary crack with poor heat conduction. Etched. Scale bar 300 J.L . See also Figure 46.

facets and faces can be explained as the steps produced by in tergranular fissuring along octahedral planes of the Widmanstiitten structure. The fracture faces were somewhat smoothed during flight and are covered by fusion crusts; local pits indicate where low-melting phosphides and sulfides ablated away before the metal.

The 750 g mass, measuring approximately 12 x 5.5 x 3 em before cutting, represents an ablation sculpture intermediate between the two other masses. It is also completely covered by fusion crusts.

From the appearance it can thus be derived that (i) the fragmentation in the air followed the Widmanstiitten grain boundaries to a significant extent and (ii), after the fragmentation, the various samples suffered very different amounts of ablation, presumably due to large differences in velocity. It is not known whether additional fragments fell. The three mentioned here are difficult or impossible to reassemble to one original mass, however.

The following is based on an examination of the material in London (B.M. no. 1927, 916). Etched sections display a medium Widmanstiitten structure of straight, long (~ ~ 25) kamacite lamellae with a width of 1.10±0.15 mm. The kamacite shows numerous subboundaries decorated with less than 1 J1 phosphide precipitates, but the bound­aries are somewhat obscured by a later alteration of the kamacite. Due to shock pressures, it is converted to contrast-rich, hatched €-structures with a hardness of 300±25. Annealing effects were not observed.

Taenite and plessite cover about 25% by area, mainly as comb and net plessite and as massive wedges with either martensitic interiors or with a felt of small acicular a-platelets. The taenite lamellae are cloudy or tarnished in brown-bluish gray colors and have hardnesses of 350±30.

Schreibersite does not occur as large lamellae, but it is common as 20-50 11 wide grain boundary veinlets and as 1-50 J1 vermicular blebs in the open plessite fields, substitut­ing for '}'-particles of similar sizes. Rhabdites occasionally

Figure 1497. Sarnelia. Detail of Figure 1496. The schreibersite crystal (S) shows incipient melting and rapid solidification to a fine-grained structure (gray) with shrinkage cavities (black). It is surrounded by typical a 2 structure. Etched. Scale bar 40 J.L.

Figure 1498. Samelia (Brit. Mus. no. 1927, 916). To the left, the heat-affected a 2 zone; to the right, the unaffected shock-hatched interior. Etched. Scale bar 500 J.L.

occur as very large prisms, 20-50 11 across, in the kamacite lamellae. All phosphides are shattered, evidently due to the same shock that hardened the kamacite and taenite phases. The bulk phosphorus content is estimated to be 0.15±0.03%.

Troilite was not present in any of the sections but will undoubtedly be found when other sections become avail­able. Daubreelite occurs as scattered blebs, 20-100 J1 across, in the kamacite.

Silicates and carbides were not detected, but the chromium nitride, carlsbergite, occurs in profusion in the kamacite lamellae. The small platelets, typically 30 x 1 11 in size, form crystallographically oriented precipitates and are occasionally enclosed by late phosphide grains.

The fusion crust is composed of an exterior black oxide layer and an interior metallic layer. Inspection of the surface discloses an interlacing of fine cracks in the crust which form a net with about 10 mm masks. The cracks

follow the Widmanshitten directions, and on polished sections the cracks may be traced to depths of 2-10 mm (at least) below the surface. This shows that not only did Samelia burst into three major fragments during the deceleration in our atmosphere but that it also formed a large number of minor additional cracks. It is characteristic that all cracks follow those Widmanstiitten a - a and a - 'Y boundaries that are rich in schreibersite precipitates. Pre­sumably these boundaries were already precracked to some extent from the early cosmic event that shock-hardened the meteorite.

The oxidic fusion crust is 10-100 J1 thick and includes droplets and pockets of molten metallic material. Etching reveals a duplex structure in the oxides. It appears that

']-~• ·~ L v : {J\_.J. \ 'f'i.. :r,"i(. , :-~'V ,7.) .IYI~ - - ..: "(- 1 ' · -v:~:;;)•V.l,(.::{· · .:--..~.

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Figure 1499. Samelia (Brit. Mus. no. 1927, 916). Detail of the transition from the heat-affected a 2 zone to the shock-hatched interior. A cloudy taenite lamella shows, at top, slightly mosaic structure. Compare Figure 114. Etched. Scale bar 50 J.l .

Figure 1500. Samelia (Brit. Mus. no. 1927, 916). From the hea t­affected A zone with fused phosphides (page 53). Small schrei­bersite crystals along an original a- a grain boundary (G-G) have melted and penetrated along the high temperature -y-boundaries. Etched. Scale bar 40 J.l .

. • ~­~ -~ V<

~-~-. . .. ; . ,.. . ~ -. '•

r<

'

;

,

Samelia - Sams Valley 1051

' . -~ ' •

I '-;..~ /. J. '

:·-....., ) ,. ' ~- .. ,

''-~ ' ~ - ~ •/, - .. ~

) . ..

~-~· ··· _i { . ~ .; . ,.. ·~

--'~ •

Figure 1501. Samelia (Brit. Mus. no. 1927, 916). From the A zone. Two fused large rhabdite crystals in a 2 matrix. Near center, a carls­bergite platelet. To the left, plessite from which carbon diffused out­wards to produce a bainitic rim zone (black). Etched. Scale bar 50J.L.

during rapid cooling a primary wiistite became supersatu­rated with respect to oxygen and exsolved minute skeleton crystals of magnetite from solid solution. In addition, magnetite nucleated and grew upon the wiistite-metal interfaces and upon wiistite grain boundaries. The exterior part of the fusion crust is wholly composed of magnetite.

Under the oxidic fusion crust there is a 1-l 00 J1 thick laminated metallic fusion crust, composed of 1-6 layers which may be crossbedded and may pinch and swell irregularly. There are numerous tiny gasholes and globular inclusions of 0.5-20 J1 oxides in the dendritic metal.

Under the two fusion crusts the heat-affected a2 zone extends to depths of l-3 mm. It consists of serrated a2

units which are very fine-grained (5-25 Jl) because they formed from a heavily worked shock-hardened kamacite_ The hardness is 185± 15 and decreases to 165±5 in the recovered transition zone towards the interior (hardness curve type I).

The Widmanstiitten cracks mentioned above signifi­cantly influenced the heat flow into the meteorite during the late stages of the flight. In several places the thicknesses of the a2 zone thus abruptly change (0.1-0.5 mm) because a crack runs obliquely across and prevents the smooth thermal flow into the metal.

Samelia is a shock-hardened medium octahedrite of group IliA, closely related to Rancho de Ia Pila, Merceditas, Augusta County, Juncal and Cumpas, to mention just a few which tally well both chemically and structurally_ It is entirely unrelated to Garhi Yasin which fell four years earlier in Pakistan.

Sams Valley , Oregon, U.S.A.

43°32'N, 123°0'W; 500 m

Medium octahedrite, Om. Bandwidth 0.75±0.10 mm. €-structure. HV 260±15.

1052 Sams Valley

Group I JIB. 10.23% Ni, 0.64% Co, 0.86% P, 18.4 ppm Ga, 35.1 ppm Ge, 0.017 ppm Ir.

HISTORY

Sams Valley evidently was a small shower of irons, since several individuals have been reported on various occasions. The available information is insufficient to establish the extent of the shower with certainty, but it may be estimated that the maximum distance between individuals was about 2 km. Foote (1915) described the largest specimen, a weathered mass of 6.9 kg found at an undetermined spot about 10 miles northwest of Medford, in Jackson County. The mass was discovered on the surface about 1894 by George P. Lindley and went through several hands before Foote purchased it from E.W. Liljegran and cut it into a few large sections. A second individual, of 1 ,233 g, was acquired by the American Museum of Natural History about 1920, also from E.W. Liljegran (Reeds 1937: 618; Lange 1967). A third specimen of 1,028 g was identified in a mineral collection by Morley (1950) who performed quite a detecting job tracing down the original locality. The 1 ,028 g mass, and two more kilogram-sized specimens which apparently are now in private collections, were found about 1890 by W.M. Payne while he was panning for gold in a small gulch on his property. Morley located the "Meteorite Gulch" as a tributary of Sams Creek in Section 13, T 358, R 2-3W, corresponding to the coor­dinates given above . Lange (1967) reviewed the history and gave a map. Olsen & Fredriksson (1966) reported the phosphates sarcopside and graftonite present as inclusions in the troilite. Jain & Lipschutz (1969) saw evidence of some annealing in the specimen they examined from the Chicago collection.

DESCRIPTION

According to Foote (1915), the largest mass of 6.9 kg measured 17 x 12 x 9 em and was irregularly lenticular in shape. Foote found no fusion crust, and this was confirmed in the present reexamination of Nos. 1 and 2. The masses are significantly weathered and covered by 0.1-5 mm thick crusts of terrestrial oxides. In several places the surface exfoliates along octahedral lamellae due to corrosion. Sections perpendicular to the surface failed to reveal any heat-affected rim zones. The terrestrial age is probably quite considerable.

Etched sections display a medium Widmanstiitten structure of straight, long (~ ~ 25) kamacite lamellae with a width of 0.75±0.10 mm. The kamacite is of the shock hardened E-varie ty and has a microhardness of 260± 15. The kamacite has subboundaries decorated with 0.5-1 J1 phos­phides and apparently contains a large number of submicro­scopic precipitates. Taenite and plessite cover about 35% by area, particularly as dense, dark-etching, martensitic fields. Comb and net plessite are also common, however. If all plessite varieties are represented, the sequence through a typical field is: a tarnished, yellow taenite rim (HV 370) is followed by a light-etching martensite (HV 355); then follows a dark-etching, platy martensite , oriented parallel to the bulk Widmanstiitten structure (HV 345); the adjacent interior is a poorly resolvable, duplex a + 'Y mixture (HV 300), and then follows an easily resolvable, duplex a+ 'Y mixture (HV 270-290). Coarse comb and net plessite follow next. The sequence and hardness levels are typical for the unannealed group IIIB irons, minimum hardnesses similar to that of the kamacite lamellae being reached in the open coarse-grained plessite areas.

Schreibersite is dominant as large Brezina lamellae, typically 35 x 5 x 0.8 mm in size. They are monocrystalline but severely brecciated, and 1-50 J1 wide troilite veinlets often fill the fraCtures along the shear planes. The schrei-

COLLECTIONS bersite's hardness is 825±25. Schreibersite is also common

Philadelphia (I ,450 g end piece of No. 1 ), Harvard as 20-60 J1 wide grain boundary veins and as narrow rims (1,160 g endpiece of No.1), New York (1,090 g slice of around the troilite nodules. Many small blebs, 10-25 J1

No. 1; 895 g of No.2), Jacksonville Museum, Oregon thick, are located as island arcs outside the taenite and (about 900 g of No.3), Ottawa (662 g of No. 1), Chicago plessite fields. Rhabdites were not observed. Phosphates are (501 g of No. !), Eugene, University of Oregon (300 g of present both in the troilite nodules and as 10-50 J1 elliptical No. 2; 100 g of No.3), Amherst (73 g; probably of No.1), inclusions in the kamacite; their hardness is 340±40. The London (55 g of No.1), Los Angeles (51 g), Tempe (26 g bulk phosphorus content as determined by point counting ofNo. 1), Washington (19 g of No.1). is 0.9%, in good agreement with the analytical value.

SAMS VALLEY - SELECTED CHEMICAL ANALYSES

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Whitfield in Foote 1915 10.46 0.64 0.86 1000 560 160

Wasson & Kimberlin 1967 9.91 18.4 35.1 0.017

Smales et al. 1967 5.1 135 < 1 17.7 35 Crocket 1972 0.0097 3.0

Whitfield's analysis has been recalculated here to include the schreibersite ; the way it was presented is no longer used.

Troilite occurs as nodules ranging from 0.2-25 mm in size. They are monocrystalline and display numerous, beautiful twin lamellae due to plastic deformation. Their hardness is 250±25. All troilite and Brezina lamellae are enveloped in 0.8-1.5 mm wide asymmetric rims of swathing kamacite.

The specimens are corroded. The troilite is often converted to pentlandite or limonite, and 10-50011 wide limonitic veins penetrate to a considerable depth along Widmanstiitten grain boundaries and phosphides. Several of these cracks are probably preterrestrial and were easily accessible to ground water action once the meteorite landed.

Sams Valley is a shock-hardened medium octahedrite which structurally and chemically is closely related to Augustinovka, Chupaderos, Sanderson and Mount Edith.

Since the annealed structure reported by Jain & Lipschutz {1969) appears confusing in a small meteorite which otherwise displays shock-hardened structure, I asked permission to examine their material (Chicago No. 1976, a 501 g slice).

The primary structure is as described above, but a secondary rt!heating has altered both the kamacite and the taenite lamellae. Of t~e kamacite, 80% is recrystallized to unequilibrated serrated grains, 5-3011 across. Somewhat larger recrystallized grains ~re found in the Ni-poor and P-poor zones adjacent to large schreibersite lamellae. The tarnished taenite is imperfectly homogenized to a yellow structureless taenite. The microhardness of the kamacite has dropped 50-100 units; that of the taenite, about 50 units.

The reason for the annealing is clear: it is due to an artificial inhomogeneous, reheating, to 400-600° C for a brief period of perhaps half an hour.

The evidence for this lies in the altered terrestrial corrosion products. On a well polished section, 1-1011 wide, high temperature reaction zones can be identified along the corroded grain boundaries and along the corroded a-schrei­bersite interfaces.

It thus appears that one of the major specimens of the Sam's Valley shower was subjected to reheating by the discoverers without this having been noted in subsequent reports.

Specimen in the U.S. National Museum in Washington:

19 g part slice (no. 510, 3 x 1 x 0.6 em)

Sams Valley - San Angelo 1053

San Angelo, Texas, U.S.A.

31°22'N, 100°26'W; 580 m

Medium octahedrite, Om. Bandwidth 0.95±0.10 mm. Distorted Neumann bands. HV 270±30.

Group IliA. 7.65% Ni, 0.50% Co, 0.10% P, 19.2 ppm Ga, 39.3 ppm Ge, 7.8 ppm Jr.

HISTORY

A mass of 88 kg was discovered in 1897 by John Johnson while he was riding horseback in search of cattle on the prairie seven miles south of San Angelo, Tom Green County. The meteorite was partially buried on the " Lipan Flats," a body of land entirely devoid of vegetation -without even mesquite trees. The mass came to the University of Texas, Austin, and shortly afterwards about two-thirds of it was acquired by Ward's Natural Science Establishment, sliced up and distributed. Preston {1898a) described the find and gave two figures of the exterior and two of the cut slices. Ward (1904a: 105, plate 2) gave two similar photomacrographs, and Mauroy ( 1913 : plate 3) gave another photomacrograph. Jaeger & Lipschutz (1967b) estimated the altered kamacite to correspond to shock pressures of 130-400 k bar. Vilcsek & Wanke (1963) esti­mated a cosmic ray exposure age of 480±50 million years, while Voshage (1967) found 580±80 million years. Various noble gases were determined by Hintenberger et al. {1967).

COLLECTIONS

Austin (about 30 kg), Chicago (5.88 kg), Washington (3.33 kg), Vatican (977 g), Gottingen (971 g), New York (933 g), Tempe (928 g), London (922 g), Tiibingen (473 g), Paris ( 430 g), Vienna ( 418 g), Harvard (295 g), Amherst (270 g), Calcutta (219 g), Leningrad (211 g), Bonn (195 g), Stockholm (181 g), Prague (I 77 g), Budapest (165 g), Canberra {152 g), Los Angeles {142 g), Oslo (142 g), Copenhagen (99 g), Moscow (82 g), Dresden (67 g), Yale 66 g), Sydney (24 g), Ottawa (24 g).

DESCRIPTION

According to Preston (1898a), the oblong mass, shaped like a large loaf, had the dimensions 51 x 29 x 14 em and weighed 88 kg. It was corroded and in some places was covered by terrestrial oxides 5-6 mm in thickness. ntis was confirmed in the present study where no fusion crust and

SAN ANGELO - SELECTED CHEMICAL ANALYSES

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Lovering et al. 1957 0.53 100 181 8.7 39 Wasson & Kimberlin

1967 7.68 I 19.2 39.3 7.8 Nishimura & Sandell

1964 0.10 I

3 Moore et al. 1969 7.62 0.48 140 585 180

1054 San Angelo -San Cristobal

Figure 1502. San Angelo (Prague no. 267; 118 g). A medium octahedrite of group IliA with a slightly distorted structure. Deep-etched. Scale bar 20 mm.

no heat-affected a 2 zones could be identified. It is esti­mated that, on the average, 3 mm of the surface has been lost by corrosion.

Etched sections display a medium Widmanstiitten structure of slightly undulating, long c{v ~ 25) kamacite lamellae with a width of 0.95±0.10 mm. The kamacite shows an abundance of subboundaries, often accumulated in dense, subparallel tangles and walls against high angle boundaries or inclusions. Neumann bands are common. They are distorted by plastic deformation, particularly around the numerous fissures where lenticular deformation bands are also common. The hardness is 270±30, indicating an uneven -but significant - cold working of the matrix.

Taenite and plessite cover about 40% by area, mainly as degenerated, open-meshed, comb and net plessite fields. The taenite framing the fields is frequently discontinuous, and many net plessite fields are nothing else than kamacite cells with a few taenite blebs in the boundaries. Some fields are sheared and kneaded in a violent fashion, and fissures normally extend far from the deformed areas. A typical dense field, 1 x 0.5 mm in size, will show a tarnished taenite rim (HV 320±20) followed by an indistinct, mar­tensitic transition zone (HV 400±25). Then follow black­etching, duplex, unresolvable a+ 'Y mixtures with a few 1 11 wide kamacite spindles (HV 350±20) and, finally, in the center a poorly resolvable a+ 'Y mixture (HV 320±15).

On several specimens, e.g., U.S. National Museum No. 256, the plastic deformations are visible to the naked eye. Sharply delineated shear zones, less than 0.1 mm wide, cut across the Widmanstiitten pattern and displace the struc­tural elements 1-2 mm. Fissures, 0.1-1 mm wide, extend 6 em and more from the violent shear zones, and some shear appears also to be present along the fissures. The deformations resemble what is described in Descubridora, Russel Gulch, Puquios, Sacramento Mountains and others, and they are preatmospheric, probably due to "geologic" events on the parent body. The structures do not corres­pond very well to the E-structures associated with "clean" shock events, although the hardness is surprisingly high and of the right order for a shock-hardened meteorite.

Schreibersite is almost absent; only a few, scattered, 2-1011 wide blebs in the grain boundaries or inside the plessite fields are encountered. Rhabdites, 0.5-2 11 across, are common in some a-lamellae. Oriented, hard platelets of chromium nitrides (carlsbergite), are common as 20 x 1 11 rose-colored, slightly distorted bodies in the kamacite phase.

Troilite occurs as nodules, 1-25 mm in size, and as elongated bodies, typically 10 x 1 mm in size. Small troilite satellites are located in a zone around the large troilite nodules. A 4 x 1 mm troilite nodule could be examined in a polished section. It is monocrystalline but severely de­formed by plastic deformation and shows undulatory extinction. Locally, along shear zones and phase boundaries it is recrystallized to a 1-10/.1 grain mosaic. The included 10011 wide, parallel daubreelite lamellae constitute about 10% by area, and these are also deformed and somewhat displaced.

Daubreelite also occurs as scattered 25-10011 wide blebs in the kamacite phase. Some are composed of alternating, very thin lamellae of troilite and daubreelite.

The corrosive attack has particularly followed the numerous fissures already present when the meteorite arrived. The fissures are anywhere from 1011 to 3 mm thick and are now partially filled with laminated, terrestrial oxides. Selective corrosion is present in the subboundaries and around the rhabdites near the surface. The troilite is veined by pentlandite.

San Angelo is a deformed medium octahedrite which is related to Kalkaska, Madoc, Merceditas, Russel Gulch and Sacramento Mountains. It has much in common with Russel Gulch in particular. Chemically, it is a typical group IliA.

Specimens in the U.S. National Museum in Washington:

493 g part slice (no. 256, 11 x 5.5 x 1.2 em) I ,900 g full slice (no. 589, 28 x 12 x 0.7 em). Figured by Preston

(1898a: 271) 29 g part slice (no. 2570, 5 x 3 x 0.2 em) 60 g slice (no. 3034,5 x 3 x 0.8 em)

798 g part slice (no. 3035, 13 x 10 x 0.8 em) 4 7 g part slice (no. 3036, 3 x 3 x 0.8 em)

San Cristobal, Antofagasta, Chile

23°26'S, 69°30'W; 1,920 m

Polycrystalline , nickel-rich ataxite, D. Significant troilite-silicate­graphite-cohenite inclusions.

A high-nickel end member of group I. 25.6% Ni, 1.0% Co, 0.18% P, about 4% S, 11 ppm Ga, 26 ppm Ge, 0.3 ppm Jr.

HISTORY

This locality was briefly mentioned by Wiilfing (1897: 404) who reported that an 82 g mass had been found in the gold mining district of San Cristobal. Cohen (1898b; 1905: 132) added that the mineral collector, Dr. The odor Hohmann, had brought a total of seven masses (or

.­Figure 1503. San Cristobal (Vienna no. H3285). Polycrystalline nickel-rich ataxite with large troilite-silicateilraphite-cohenite inclu­sions. Deep-etched. Scale in centimeters.

fragments) to Budapest and Vienna in 1896; the largest block weighed 3,670 g while the six smaller ones ranged from 30 to 80 gin weight. He estimated the total recovered weight to be 4.0 kg and gave Caracoles as a synonym for the locality. The set of coordinates given above is the best available; it pinpoints the San Cristobal mine as deduced from modern geological maps.

BerVIerth (1914: 1062) discussed the microstructure, and Pfann (1918) explained it on the basis of the then-current Fe-Ni-system, exhibiting a eutectoid point at about 18% Ni. Pfann also presented three photomicro­graphs of the pearlitic structures which he believed had formed by a eutectoid decomposition similar to that occurring in steel at 720° C.

Owen & Burns (1939) and Owen (1940) examined the microstructure by X-ray diffraction, but their results are difficult to interpret. Perry (1944: plates 29 and 30) presented a series of excellent photomicrographs, clearly showing the pearlitic structure which is present in limited areas of some grains.

COLLECfiONS

Vienn a (about 1.5 kg slice; 16 x 10 x 1.2 em), New York (852 g endpiece; 15 x 8 x 2.5 em), Washington (135 g), London (135 g), Chicago (114 g), Budapest (62 g), Copenhagen (32 g), Greifswald (14 g), Bonn (14 g), Berlin (8 g).

San Cristobal 105 5

DESCRIPTION

The original dimensions of the main mass can be reconstructed to have been 16 x 10 x 8 em. It is not clear whether the six small specimens are individuals with fusion crust or are fragments detached from the main mass by the discoverers . The last possibility is more plausible, since San Cristobal is a very intricately sculptured mass from which material could be broken along the grain boundaries.

The main mass is richly sculptured with many cavities and depressions that are generally 1-3 em in diameter and 1-3 em deep. Most of them are cavities from troilite that burned out during the atmospheric flight. The metal stands out in ragged relief as horns and knobs between the cavities. The metallic surface is relatively smooth, and in many places a little fusion crust is still preserved, albeit in a limonitized form . It is estimated that on the average less than 0.5 mm is lost by terrestrial weathering. The corroded metal forms 0 .1 -0.5 mm thick limonite crusts and impreg­nates the ocher colored caliche that covers part of the surface.

Etched sections display an unusual structure which, on the whole, is different from all other meteorites but, in detail, shows many connections to the coarse octahedrites of group I, such as Canyon Diablo. San Cristobal is a poly crystalline aggregate of taenite and troilite crystals. The taenite crystals are each 15-30 mm in diameter and slightly differently oriented. The troilite fills in the grain bound­aries or forms 5-15 mm rounded or lobed units. Troilite covers from 10 to 20% of the available sections, so it is easy to understand the roughly sculptured surface as having been caused by the burning out of troilite . In several places a little troilite is still preserved at the bottom of the pits.

Where the metallic grains are not separated by troilite, they join along boundaries marked by the precipitation of 5-5011 wide, discontinuous kamacite bands or by schrei­bersite veinle ts of similar dimensions. A 0.1-0.3 mm wide zone along the boundaries consists of a soft taenite -which has not decomposed - with a hardness of 240±20. Then follows a zone with numerous, tiny kamacite platelets (1-3 11 thick) and finally comes the grain interior where the kamacite-precipitates are coarser (5-15 11 thick). The plate­lets are straight and oriented along the normal Widmanstiit­ten directions; they are usually ten times as long as wide. In contrast, a number of irregular kamacite patches, 10-30 11 across, have developed by heterogeneous nucleation around scattered schreibersite blebs. The kamacite has a microhard­ness of 180±10, and constitutes about 5% by area. The

SAN CRISTOBAL - SELECTED CHEMICAL ANALYSES

percentage References Ni Co p

I c Sjostrom in Cohen

1905 25.6 1.00 0.18 Smales et al . 1967 Wasson 1967a 25 Crocket 1972

s Cr

6.7

Cu

1016

ppm Zn

22

Ga Ge Ir Pt

10 29 11.9 25.8

0.34 <0.5

105 6 San Cristobal

" \ \ ( . I; -Figure 1504. San Cristobal. The opposite side of Figure 1503. The exterior sculpture is from ablation in the atmosphere. The individual precursor taenite grains show either a pearlitic or a martensitic development. Deep-etched. Scale in centimeters.

Figure 1505. San Cristobal (New York no. 2229). Detail of one of the pearlitic areas. A small finely lamellar area is surrounded by a coarser structure. Kama cite is gray; taenite, white . Etched. Scale bar 400 Jl.. (Perry 1944: plate 29.)

remaining 95% is taenite which is partially decomposed to martensitic-acicular structures with hardnesses of 350±10.

Overetching causes numerous black stains to develop in the taenite-martensite areas. It is not clear why this is so. On the other hand, the phenomenon appears to be closely related to the black, lobed patches which develop by overetching upon normal high-nickel, high-carbon plessite fields in Bahjoi, Bogou, Canyon Diablo and numerous other group I meteorites. The black patches in San Cristobal are between 10 and 100 11 in size and sometimes cluster to larger units. They are intermediate (HV 310±30) between taenite and acicular martensite in hardness, and the hardness impression itself is of the characteristic pincushion shape in contrast to the regular square or barrel shape in the martensite. Perhaps the main difference between the dark stained areas and the martensite is that the dark areas represent diffusional decomposition of taenite to submicro­scopic lamellar intergrowths of a and 'Y, while the mar­tensitic areas have decomposed in a diffusionless manner. In addition there may be small differences in the carbon content.

About 5% of the austenite grain area has transformed to beautiful, pearlitic structures. Within as much as 10 x 10 mm, the lamellae are subparallel, being taenite

0 ~ '-J J 111 0 ·'"~J~ 0 • ~ v "

.¢/.,{, , , ~ '· fl g ~" • do;J f'<l / '. ·~" Qo ,ij ., "'P~ \ ~

if" ?! ~ ~ 3 c '':!-) ~ """"

IJ

'\

J>• - , ··•~;.. " U. , ' . ,!/ 1 """ , ~ , dey-£:?? &"'i ~~ p, JYI\.• 7 0 IJ- '1J? f' ~ -""' \ ' • "',_";(>P ~ ~ ~ ' , ~ '25 0~ ~{). 0 ., \) /;~ " > P' <? ' ' :>~ ~

. - . "' ' " ~ ~ ' . \• ' 't: \ • '"' - ,. 1 D. o ~f ~ :~_.,:, \,, ~Y~-. ;o ,

A • ""'~'•'# ~ j ' · 'r lo,• "'~-,.~,.\#o, _ , '\~·· I " ctJ~' ~~ ~ "';;.~ ,' '0· '?}(' ~ '«,}fA,;"" , . " ~- . ~--~· ' . . - ~, . /'"•

" ? . .,. ' I' ~. . " . . , • ..,.n '{o " , \l "' · 'q . / 1 · ,:y '' "" - ,W •• •4 ° ' I • '"" ·kf: • ' ' Pf' \ ,, . • f ""'P ". , ~ ~ &7 ... ' . "' p-- ~ \~

/ . ' fJ .,. ~ ~ ft,..J ' ~ ~ . . () o,_

Figure 1506. San Cristobal (Copenhagen no. 1905 , 1751). Detail of one of the martensitic-acicular areas. Very fine a-spindles occur in profusion in a Widmanstiitten pattern. Compare Figure 1507. Lightly etched. Scale bar 200 IJ..

(HV 300±25) and kamacite (HV 180±10), respectively. Along the transition zone to the main areas, described above, the pearlite has narrow taenite lamellae, generally only 1 J1 thick, but towards the center the taenite increases to 20 J1 or more in width. The taenite of the pearlite is fairly homogeneous with no indications of martensitic or duplex structures.

Cohenite is present as spongy , fibrous intergrowths with the pearlite, mainly in the fine-grained transition zones. The cohenite attains arm widths of 50 J1 and has a microhardness of I 050±30. It incorporates tiny blebs of schreibersite. Cohenite , and some haxonite , are also found as scattered blebs, 5-50 J1 across, in the martensitic parts of the grains.

It has generally been assumed (Brett 1967) that cohenite - and carbides in general - are restricted to meteorites containing from 6 to 8% Ni; however, as repeatedly shown in this work, carbides occur as accessory minerals in hexahedrites as well as in fine octahedrites and some ataxites. These observations extend the range from 5 .5% Ni to 29% Ni so that it actually covers almost all possible iron meteorites. It appears, on the other hand, that cohenite in significant amounts - as easily distinguishable crystals - occurs only in group I and associated meteorites.

Schreibersite is ubiquitous as irregular blebs, ranging from 2-20 J1 across. Many of them have served as nuclei for kamacite precipitation. Millimeter-sized schreibersite crys­tals occur locally.

The troilite is interesting because it is of the complex nodule type which normally is only associated with group I irons, such as Canyon Diablo and Pitts. The troilite is monocrystalline but contains numerous inclusions of olivine and pyroxene, either as individualS0-100 J1 grains or as loose clusters. Also scattered phosphate crystals are present. Graphite occurs along the troilite rim as 100-500 J1 irregular bodies, composed of radiating sheaves with horse­tail extinction. The palinate-like complexes are sheathed in

San Cristobal- Sanderson 1057

Figure 1507. San Cri stobal (New York no. 2229). A martensitic­acicular area similar to Figure 1506. Upon heavier etching the martensitic matrix develops while the kamacite spindles etch black and are hardly to be seen. Scale bar 200 IJ. . (Perry 1950: volume 4.)

20-150 J1 thick schreibersite rims followed by discontin­uous, 20-50 J1 thick cohenite rims. Around the whole is a 50-200 J1 wide zone of swathing kamacite and then follows undecomposed taenite. It may be noted that these nodules are exact miniatures of the nodules in Canyon Diablo.

San Cristobal is a nickel-rich ataxite which exhibits remarkable structural and textural associations with group I. If bandwidths are plotted versus nickel on graphs, or gallium versus nickel, or germanium versus nickel , San Cristobal falls on the smooth, extrapolated curves of group I. Such behavior is usually considered sufficient for assigning an unknown iron to a chemical group. Since the polycrystallinity and, in particular, the troilite-graphite­silicate inclusions and the cohenite accessories are also common characteristics of group I and San Cristobal, I will conclude that the meteorite forms an extreme member of group I.

Specimens in the U.S. National Museum in Washington:

127 g endpiece (no. 3037 , 6.5 x 4 x 1.5 em) 8 g polished slice (no. 3039)

Sanderson, Texas, U.S.A.

30°8'N, 102°9'W; 700 m

Medium octahedrite, Om. Bandwidth 0.75 ±0. 10 mm. Neumann bands. HV 215±15.

Group IIIB. 9.81% Ni, 0.50% Co, 0.6% P, 18.2 ppm Ga, 35.8 ppm Ge, 0.021 ppm Jr.

HISTORY

A mass of 6.8 kg was found in. l936 near Sanderson, in Terrell County , according to A.D. Nininger (1940). Accord­ing to Curator W.S. Strain of the College of Mines and Metallurgy in El Paso (the present University of Texas at El Paso) the mass was found by Hugh Rose at a point about

1058 Sanderson

15 miles east of Sanderson (H.H. Nininger, personal communication). The coordinates given above correspond to this locality. Most of the mass was acquired by Nininger about 1940, and it was cut and somewhat distributed. It has been classed as a fme octahedrite (Nininger & Nininger 1950: 92, plate 5) with a bandwidth of 0.57 mm (Nininger in Goldberg et al. 1951 ), and as a medium octahedrite (Goldberg et al. 1951) with a bandwidth of 1.25 mm (Hey's Catalog 1966: 425). My observations indicate that it is a medium octahedrite with a bandwidth of 0.75 mm. Jaeger & Lipschutz (1967b) found preferred orientation of the kamacite by X-ray diffraction studies, suggesting shock levels of 130-140 k bar. Schultz & Hintenberger (1967) examined the amounts of noble gas isotopes. Voshage (1967) reported a «xj41K cosmic ray exposure age of 590±90 million years. Burnett & Wasserburg (1967a) ex­tracted a minute silicate inclusion, probably mostly olivine, and examined the rubidium and strontium contents.

COLLECfiONS

Tempe (2,200 g), London (1,708 g), Washington ( 471 g), Chicago (335 g), Ann Arbor (288 g).

DESCRIPI'ION

The mass is roughly lenticular with the average dimensions of 18 x 12 x 8 em; it weighs 6.8 kg. It is partly covered with yellow-brown caliche deposits, under which are 0.1-0.5 mm thick crusts of terrestrial oxides. Neverthe­less, the fusion crust is preserved in several places as a 50-100 J1 thick magnetite-wiistite layer; also, a 1-2 mm

thick, heat-affected a 2 zone is present along most of the circumference of prepared sections. Micromelted phos­phides are found in the exterior 20-50% of the heat­affected zone.lt is estimated that, on the average, not more than 0.5 mm of the mass has been lost by weathering. The microhardness of the a 2 zone is 187±8 (hardness curve type II).

Etched sections display a medium Widmanstiitten structure of somewhat irregular, straight (W- 15) kamacite lamellae with a width of 0.75±0.10 mm. The kamacite shows indistinct Neumann bands which are frequently distorted , and the microhardness is 215±15. It increases about 50 units in areas where the kamacite is cold-worked around sheared schreibersite crystals. Subboundaries with 0.5-1 J1 thick phosphide precipitates are common, and further phosphide precipitates, about 0.5 J1 across, are very common everywhere in the kamacitic matrix.

Taenite and plessite cover about 35% by area; particu­larly common are comb plessite and taenite wedges the interiors of which show various stages of martensitic transformation. The tarnished, yellow taenite border (HV 350±20) is followed by brown martensite plates, precipitated parallel to the bulk Widmanstiitten directions (HV 350±20); the interior, duplex a+ 'Y fields have hard­nesses which are inversely related to their fineness : about 325 for fme-grained, almost unresolvable, material and 230 for coarse-grained material with 2-3 J1 wide taenite blebs.

Schreibersite and troilite dominate the available sec­tions in much the same way as in Bella Roca, Chupaderos, and Augustinovka. The schreibersite forms 15 x 5 x 1 mm Brezina lamellae in dodecahedral planes of the parent taenite. It is monocrystalline but brecciated, and the shear zones are often filled with 1-25 J1 wide, injected troilite melts. The microhardness of the schreibersite is 925±25. Schreibersite is further common as 10-50 J1 wide grain boundary veins, as 5-50 J1 blebs inside the plessite, and as island arcs of 10-20 J1 thick blebs located just outside the taenite and plessite phases. Rhabdites proper were not observed, but, as mentioned above, the matrix is loaded with almost submicroscopic phosphide particles. Point counting indicated a bulk phosphorus content of 0.6%, in good harmony with the analytical value.

The troilite forms rounded nodules, 10-30 mm across, but smaller blebs, 0.1-0.5 mm across, are also well distrib­uted. The troilite nodules are often indented by 2-5 mm metal tongues which display Widmanstiitten structure. The

Figure 1508. Sanderson (fempe no. 441.3). Medium octahedrite of nodules have nucleated a rim of 0.1-0.6 mm thick schrei-group IIIB. Brezina lamellae of schreibersite and large nodules of troilite. Swathing kamacite is well developed around both minerals. bersite which, in tum, has nucleated asymmetric, Deep-etched. Scale bar approximately 3 em. 0.1-1.5 mm wide rims of swathing kamacite. At least the

SANDERSON - SELECfED CHEMICAL ANALYSES

percentage ppm References Ni Co p c s Cr Cu Zn Ga Ge Ir Pt

Wasson & Kimberlin 1967 9.87 18.2 35.8 0.021

Lewis & Moore 1971 9.75 0.50 0.59 50

smaller troilite inclusions are shock-melted and solidified to 1-10 J1 aggregates, often including 1 J1 particles of metal in a eutectic structure. The troilite rims are frayed and several fissures extending from the nodules into the metal are filled with injected troilite melts.

In the kamacite there are several, rounded , bluish-gray, almost isotropic inclusions; which may be phosphates.

Sanderson is a medium octahedrite of group IIIB which is related to Kouga Mountains, Chupaderos, Bear Creek, Augustinovka and Sam's Valley. Its detailed structure suggests some shearing at both high temperature and later at low temperature. The last deformation may have been the result of a relatively mild shock followed by negligible annealing. Its terrestrial age may be of the same order as Chupaderos, estimating from the state of preservation.

Specimen in the U.S. National Museum in Washington:

471 g slice (no. 1405, 13 x 7.5 x 0.8 em)

Sandia Mountains, New Mexico, U.S.A.

Approximately 35° 15'N, 106° 13'W; 1800 m

Coarsest oetahedrite, Ogg. Bandwidth 10±5 mm, and 3 em grains. Neumann bands. HV 210± 10.

Group liB. 5.90% Ni, 0.49% Co, 0.40% P, 59 ppm Ga, 174 ppm Ge, 0.14 ppm Jr.

HISTORY

In 1927 a small fragment of 90 g was sent to Nininger for examination. It was said to have come from a mass of about 100 pounds, found in 1925 in the Sandia Mountains northeast of Albuquerque, but later lost. Nininger {1929b) described the badly hammered fragment and gave two photomacrographs. Evidently, briefly afterwards he tracked down a substantial part of the main mass, for in his catalog (1933a) he lists the possession of 10.3 kg slices and states that the known weight was 15 kg. In a letter to the author Dr. Nininger comments:

" . .. Finally I found a man with about 15 kg which I purchased. He said this 15 kg mass was about half of the original and that pieces had been detached and given to friends. As near as I could determine by considerable

Sanderson - Sandia Mountains 1059

field work the mass had been found near the village of Golden in the Sandia Mountains."

The coordinates above are for Golden. Perry (1944: plate 1) reproduced a photomacrograph which clearly showed the very coarse octahedral structure, and Nininger & Nininger {1950: plate 11) and Nininger (1952a: plates3 and 4) gave additional structural pictures that brought out the octahedral arrangement of individual grains. La Paz {1965: 111) noted that intense searches for the main mass had been fruitless. Bauer (1963) determined the 3 Hef4He ratio and estimated the cosmic ray exposure age to be 140 million years. Lipschutz et al. (1965) found it greater than 210 million years by the 21Nej26Al method.

COLLECTIONS

Tempe (6,647 g), Washington (1 ,672 g), Harvard (765 g), Denver (about 750 g), Albuquerque (536 g), Chi­cago (460 g), London (459 g), Los Angeles (60 g), New York (57 g), Ann Arbor (40 g), Yale (10 g).

DESCRIPTION

The half mass acquired by Nininger looked like one half of a melon-shaped individual. The specimens in the U.S. National Museum are covered by a crust of terrestrial oxides, 0.1-2 mm thick. No fusion crust or heat-affected a2 zone could be identified, so it is estimated that at least 3 mm of the surface is removed by terrestrial corrosion. The corrosion penetrates particularly along the grain boundaries which are lined with phosphides. The meteorite will break rather easily along these boundaries which are now filled with 0.1-2 mm wide limonitized veins.

Etched sections display a coarsest Widmanstiitten structure which is frequently interrupted by large irregular kamacite grains developed around schreibersite-troilite in­clusions. The kamacite width may be estimated to be 10±5 mm, and the individual lamellae attain lengths of 8 em; the octahedral arrangement of the finger-sized lamel­lae is best observed on broken fragments. The parent taenite was clearly a single crystal.

The kamacite has numerous subboundaries decorated with 0.5-2 J1 rhabdites; the subboundaries form extremely

SANDIA MOUNTAINS - SELECTED CHEMICAL ANALYSES

References

Hawley in Nininger 1929b

Henderson 1941c Goldberg et al. 1951 Lovering et al. 1957 Nichiporuk and Brown

1965 Smales et al. 1967 Wasson 1969

Ni

5.75 5.92 5.94

5.85

percentage Co p c s

0.39 0.23 400 400 0.53 0.68 0.53 0.49

ppm Cr Cu Zn Ga Ge Ir Pt

-

200 800

56.5 25 123 53 143

<0.4 9.0 26 124 184

59.0 174 0.14

1060 Sandia Mountains - Sandtown

Figure 1509. Sandia Mountains (U.S.N.M. no. 855). Coarsest octa­hedritc of group liB. The Widmanstiitten pattern, although coarse, is obvious. Skeleton schreibersite crystals are common (S). Deep­e tched. Scale bar 30 mm. S.I. neg. 33685B.

dense tangles of subparallel lines near schreibersite, other­wise they are normally developed. Neumann bands are common; they are up to 10 JJ. wide in clear kamacite with large rhabdites, but only about 1 JJ. wide in kamacite with dense clouds of 0.5-1 JJ. rhabdite precipitates. This suggests that the major precipitation had taken place when the Neumann band-forming event took place - that is, the mass was at least below some 300° C. Later a gentle annealing has partially eliminated many of the Neumann bands; they are faintly decorated with< 0.5 JJ. precipitates, and they are interrupted in places, giving way to tangles of subbound­aries. The microhardness is 210±10.

Taenite and plessite are very scarce, occurring only with one 0.2-0.4 mm field per 10 cm 2 • One particular field , in a grain boundary, consisted of taenite with scattered, 1 JJ. wide kamacite needles in the interior. The martensitic transition zone had a hardness of 380, while the interior had a hardness of 295. The taenite rim itself was too narrow for measuring.

Schreibersite is common as 25 x .3 or 10 x I mm skeleton crystals and as O.I mm wide grain boundary veinlets. In several places schreibersite, kamacite and troilite form pockets, e.g., 3 x 2 x 1 em in size, of what appears to be coarse eutectic structures. They are similar to structures observed in Summit, Sao Juliao and other irons of group liB, but perhaps less frequent. The schreibersite is monocrystalline and has a microhardness of 900±25. In a zone, 2-5 mm wide, around the schreibersite only very small rhabdites, 0.5-I JJ. across, have precipitated. Farther away, the rhabdites attain cross sections of 5-15 JJ., some­times occurring as branched units. By point counting of sections totaling 485 cm2 , the bulk phosphorus content was estimated to be 0.40%, in reasonable agreement with the average of the two published, analytical values.

Troilite occurs as 1-10 mm nodules and elongated bodies, particularly as the central part of clusters of schreibersite crystals. The troilite is monocrystalline and contains about 10% daubreelite as angular blocks and lamellae. Chromite is present as rather large euhedral

crystals. In one place three cubic crystals, from 4-6 mm in size, were associated with a coarse troilite-schreibersite­metal eutectic.

Cohenite, another accessory mineral, covers the large schreibersite crystals with discontinuous, SJif> JJ. thick rims.

Sandia Mountains is structurally related to El Burro, Ainsworth, Iredell, and Mount Joy and is a typical member of group liB. See also New Mexico.

Specimens in the U.S. National Museum in Washington:

I ,190 g slice (no. 855, 16 x 10 x 1.3 em) 30 g fragments (no. 855) 40 g hammered, detached kamacite grain (no. 2292, 2 x 2 x

1.5 em) 412 g part slice (no. 2292, 13 x 6 x 0.8 em)

Sandtown, Arkansas, U.S.A.

35°56'N, 91°38'W; ISO m

Medium octahedrite, Om. Bandwidth 1.20±0.20 mm. Annealed, duplex 01 + -y. HV 200±8.

Group IliA. 8.09% Ni, about 0.2% P, 21.0 ppm Ga, 41.4 ppm Ge, 1.4 ppm Jr.

Originally listed as Joe Wright Mountain No.2.

HISTORY

A mass of 9.4 kg was found in 1938 in Independence County, the same county in which Joe Wright Mountain was found in 1884. Therefore, it was tacitly assumed that it was a second fragment of Joe Wright Mountain, and it was listed as such (Nichols 1939; Horback & Olsen 1965: 239; Hey 1966: 222). Inasmuch as the new locality - Sec­tion 21, Township ISN, Range 6W - places the fmd about 20 km northwest of the original find, I suggested to Dr. E. Olsen of the Field Museum that the 9.4 kg mass be cut in order to test my hypothesis that the two irons were different. The present examination confirms that the two masses are independent falls. They have different structures

Figure 1510. Sandtown (Chicago no. 2265). Degenerated comb plessite and annealed, duplex kamacite. Etched. Scale bar 300 J.L.