Tourmaline EOSC 220 – November 23, 2004. Trigonal – Ditrigonal Pyramidal Table 2. Additional...
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Transcript of Tourmaline EOSC 220 – November 23, 2004. Trigonal – Ditrigonal Pyramidal Table 2. Additional...
Tourmaline
EOSC 220 – November 23, 2004
Trigonal – Ditrigonal Pyramidal
Hardness (Mohs)
7 to 7.5
Specific Gravity 3.06 (+ 0.20; - 0.06)
Crystal System Hexagonal-trigonal
Colors Any and all. Tourmaline occurs in more colors than any other gem. Some colors have specific variety names, including:
• Bi-color: More than one color in the same stone • Chrome: Intense green, colored by chromium and/or
vanadium • Indicolite: Blue • Paraíba: Electric blue to green, colored by copper • Rubellite: Red • Watermelon: Pink in the center, green at the edge
Pleochroism Strongly dichroic with the ordinary ray having a darker color
Dispersion 0.017
Phenomena Cat's eye tourmalines are common. Color-change chrome tourmalines, which change from green to red, are occasionally found.
Tourmaline Group
Tourmaline Groups
Table 1. Current tourmaline end member species accepted by IMA
Species(X) (Y3) (Z6) T6O18 (BO3)3 V3 W
Alkali tourmaline
ElbaiteNa Li1.5 Al1.5 Al6 Si6O18 (BO3)3 (OH)3 (OH)
Schorl Na Fe2+3 Al6 Si6O18 (BO3)3 (OH)3 (OH)
Dravite Na Mg3 Al6 Si6O18 (BO3)3 (OH)3 (OH)
Olenite* Na Al3 Al6 Si6O18 (BO3)3 (O)3 (OH)
Chromdravite
Na Mg3 Cr6 Si6O18 (BO3)3 (OH)3 (OH)
Buergerite
Na Fe3+3 Al6 Si6O18 (BO3)3 (O)3 F
Povondraite*
Na Fe3+3 Fe3+
4Mg2 Si6O18 (BO3)3 (OH)3 O
Vanadiumdravite
Na Mg3 V6 Si6O18 (BO3)3 (OH)3 (OH)
Calcic tourmaline
Liddicoatite*
Ca Li2Al Al6 Si6O18 (BO3)3 (OH)3 F
Uvite* Ca Mg3 MgAl5 Si6O18 (BO3)3 (OH)3 F
Hydroxy-feruvite*
Ca Fe2+3 MgAl5 Si6O18 (BO3)3 (OH)3 (OH)
X-site vacant tourmaline
Rossmanite
LiAl2 Al6 Si6O18 (BO3)3 (OH)3 (OH)
Foitite* Fe2+2Al Al6 Si6O18 (BO3)3 (OH)3 (OH)
Magnesiofoitite
Mg2Al Al6 Si6O18 (BO3)3 (OH)3 (OH)
* These end-members are modified from the original suggested formulae to produce proper end-members (Hawthorne and Henry, 1999).
Buergerite
• NaFe+3Al6(BO3)3Si6O21F
• in cavities in a rhyolite • Bronze, Dark brown, Black • From near Mexquitic, San
Luis Potosi, Mexico
Chromdravite
• NaMg3(Cr,Fe+3)6(BO3)3
Si6O18(OH)4
• Greenish black, Dark green
• Onega trough, Karelia Republic, Northern Region, Russia
Dravite
• NaMg3Al6(BO3)3Si6O18(OH)4
• Metasomatically altered magnesian or dolomitic limestones in contact-metamorphic aureoles
• Black, Green, Red, Blue, White
• Drava River, Austria
Feruvite
• (Ca,Na)(Fe,Mg,Ti)3(Al,Mg,Fe)6
(BO3)3Si6O18(OH)4
• Brownish black, Dark brown, Black
• Repanga Island (Cuvier Island), Waikato, North Island, New Zealand
Foitite
• Na<0.5(Fe+2,Al)3Al6Si6O1
8(BO3)3(OH)4
• Bluish black • California
Liddicoatite
• Ca(Li,Al)3Al6(BO3)3Si6O18(O,OH,F)4
• Blue, Brown, Green, Pink, Red
• Detrital in soil, product of pegmatites
• From Antsirabe, Tsilaizina, and Anjanabonoina, Madagascar
Olenite
• NaAl3Al6(BO3)3(Si6O18)(O,OH)4
• Light pink • Aluminum-rich
tourmaline. Forms a series with elbaite
• Decembrist pegmatite field, Olenik River Basin, Russia
Povondraite
• (Na,K)(Fe+3,Fe+2)3(Fe,Mg,Al)6
(BO3)3Si6O18(OH)4
• Black • Alto Chapare district,
Chapare Province, Cochabamba, Bolivia
Schorl
• NaFe+3Al6(BO3)3Si6O18(OH)4
• Black, Brownish black, Greenish black, Bluish black
• Granites, diorites, gabbro pegmatites, greisens, skarns and quartz veins
• Sonnenberg, Bodenmais and Spessart, Germany
Uvite
• (Ca,Na)(Mg,Fe+2)3Al5Mg(BO
3)3Si6O18(OH,F)4
• Yellowish brown, Brown, Blackish brown, Bluish black
• Pegmatitic and skarn rocks
• Province Uva, Sri Lanka
Vanadiumdravite
• NaMg3V6(Si6O18)(BO3)3(OH)4
• Dark green, Black • Accessory mineral in
metamorphic rocks with quartz and Cr-V bearing diopside
• Slyudyanka complex, Lake Baikal region, Zabaikalye (Transbaikal), Siberia, Russia
Elbaite
• Na(Li,Al)3Al6(BO3)3Si6O18(OH)4
• Blue, Colorless, Green, Yellow, White
• Granitic pegmatites characterized by hydrothermal replacement
• Island of Elba, Italy
Elbaite
Elbaite
Watermelon Tourmaline
Cat’s Eye Tourmaline
Tourmalinated Quartz
Canadian - Stargazer
Canadian – Leduc, Quebec