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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?