Post on 24-Jan-2016
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Smithsonian Mineral Collection
PyritePhoto by Chip Clark
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Chem270 Geology and the Engineer
Professor Howard L. McLeanDepartment of ChemistryRose-Hulman Institute of
TechnologySpring 2007
Day 01 Introduction to Mineral Properties for Identification
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Course Goals for Geoscience
To provide students interested in the geosciences an opportunity to examine geological data and formulate hypotheses to explain observed facts, trends, evidence and patterns.
To provide an introduction from another vantage point the reinforces SEM strategies and team collaborations.
To provide a spectrum of geologic concepts and principles that may be of interest to the proactive participant.
To provide a range of hands on activities that may prove relevant to the working engineer and / or scientist.
To provide visual methods of interpreting geologic data.
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Course resources (initial) * http://wikipedia.com * W. K. Hamblin and J. D. Howard, Exercises
in Physical Geology, 2005, 12th edition (Prentice-Hall) appendices color slides website access Chapter 2 – Mineral identification
R. M. Busch (editor), Lab Manual in Physical Geology, 2006, 7th edition (AGI NAGT)
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Course Resources websites
United State Geological Survey Indiana State Geological Survey Purdue University and Indiana University
textbooks * Groteziner; Jordan; Press; Siever; Understanding Earth, 5th ed.,
NY: W. H. Freeman & Co., 2007 Plummer; McGeary; Carlson, Physical Geology: Earth Revealed,
8th ed., NY: McGraw-Hill Book Co., 2001 Sievers; Press, Understanding Earth, NY: W. H. Freeman & Co.,
1986 Blyth, F. G. H.; de Freitas, M. H. A. Geology for Engineers, 7th
ed., NY: Elsevier Science Publishing Co., 1984
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Websites – minerals
Mineralogy: images and a data base that can be searched for minerals by name or chemical composition. http://un2sg4.unige.ch/athena/mineral/
mineral.html
Smithsonian Gem & Mineral Collection: images and descriptions of outstanding mineral specimens in the Smithsonian. http://www.minerals.si.edu/
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Mineral properties for identification
Objectives To define
mineral amorphous solid
To apply physical, chemical, optical, magnetic, fluorescent properties for the identification of minerals (and rocks)
To categorize properties into primary groups To categorize properties into secondary groups
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Properties for forensic approach of identification
physical chemical
fizz test with dilute HCl(aq) odor test with dilute HCl(aq)
optical reflection refraction (double: NaCl versus CaCO3) fluorescence transparent / translucent / opaque
magnetic crystal habit
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Physical properties (primary) hardness luster streak color (impurities) density (specific gravity) cleavage fracture tenacity
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Nature of minerals (True or false)
composed of elements or groups of elements that naturally unite
inorganic substance crystalline solid definite internal chemical structure definite proporptions of elements
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Quartz crystal habits Quartz: trigonal six-sided prism Quartz: striated prism faces Quartz: left-handed form Quartz: right-handed form Quartz: Japan twin
contact twins, two individuals nearly right angles Quartz: Dauphine twin
double right-handed or double left-handed crystals Quartz: Brazil twin
combined right- and left-handed crystals
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NAGT View on Crystal Habit
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Fracture is the tendency of a crystal to break
along irregular surfaces and independent of cleavage planes
fresh surface illustrates the true color of a mineral (caution: weathering hides color)
types of broken surfaces conchoidal fractures -- smooth, curved
surfaces -- obsidian, quartz, flint (chalcedony) fibrous splintery
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Fracture
mineral examples with various numbers of fractured surfaces (Blythe, et al., p. 63)
conchoidal even surface uneven surface hacky surface
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Is quartz, a stable and resistant rock forming mineral?
NAGT slide
Field trip
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Compare and contrast silica
silica hardness fracture luster
quartz 7 conchoidal vitreous
chalcedony
6½ conchoidal vitreous to waxy
chert
flint
opaque bands
jasper
agate 6½ conchoidal onyx
opal 5½ to 6½
conchoidal vitreous to resinous
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Crystalline versus microcrystalline
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Opal (silicon dioxide)
Silicon dioxide and water molecules.
Amorphous network.
What is a mineral?
Is glass a mineral?
Is ice a mineral?
Is oil a mineral?Photograph courtesy of NAGT.
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Streak
create a powder for a mineral and observe the resulting color on an unglazed porcelain tablet (and sometimes paper works) nonmetallic luster = white or pastel streak applicable to important non-silicate minerals if the H > 5, then scratch the porcelain plate
and may observe a white or colorless streak
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Streak diagnostic test
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Crystal habits versus cleavage? What is luster?
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What mineral specimens correspond to the following?
iron(II) oxide iron(III) oxide triiron tetroxide
fool’s gold taste sweet and is less filling
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Common iron(III) oxide
hematite (heamatite) commercial applications
jewelry paint pigments ferrofluids technology
chemical formula Fe2O3 (earth variety) Fe2O3 (metallic variety is highly polished) hydrated form = observable in specimens
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Consider appendix information for hematite
nonmetallic luster and
dark color
softer than glass~1.5 = H
cleavageversus fracture
streakred
red orangeyellow
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Common triiron(III) oxide magnetite
octahedral single crystals generally massive distribution
material science applications recording media inexpensive
chemical formula Fe3O4
actually an adduct
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Consider appendix information for magnetite
metallic luster and
dark color
harder than glass~6 = H
cleavageversus fracture
streakblack
dark gray
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Mineral specimen numbers? __
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Intermediate conclusions
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Mohs hardness scale based on common everyday objects (kit)
___ = H = fingernail ___ = H = copper penny (>1983) ___ = H = knife blade ___ = H = window glass ___ = H = stainless steel file ___ = H = porcelain streak plate ___ = H = optical glass (qtz)
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Mohs hardness scale based on common rock forming minerals
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Mohs hardness scale andNewer MS engineering scale
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Hardness scale
other examples Specimen # Specimen # Specimen # Specimen # Specimen #
relation to common objects
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Dropping acid
calcite
dolomite marble
odoriferous
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Cleavage examples (HOS)Which specimens?
calcite quartz
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How tenacious is your favorite mineral?
manner of resisting breakage (tenacity) classes examples
brittle quartz malleable native coinage metals sectile (slice) talc flexible gypsum elastic muscovite and
biotite
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Definition for tenacity __________ describes the result of cutting with a
knife and producing shavings __________ angular fragments are the result of
crushing unstable mineral __________ minerals will bend and regain its original
shape when the force is removed __________ minerals may be shaped and flattened
into a sheet without breaking __________ describes the ability of a mineral to
bend but not return to its original shape when the force is removed
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Optical properties (specimens?)
transparent (image) calcitequartzbiotite
muscovite translucent (light) CaSO4 . 2 H2O opaque Fe3O4
FeS2
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Common rock forming mineralscalcium carbonate
versus silicon dioxide
Relative hardness of calcium carbonate double refraction
Relative hardness of silicon dioxide magnification
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Halite or calcite – three clues?