Chapter 2: Properties of Minerals

Chapter Outline:

- Preview of Properties of minerals - Lab exercise - Mineral lab tour TA : Niti Mankhemthong Office Hour: Monday 12:00-13:00 Friday 11:00-12:00 @room GB326 or by an appointment Contact E-mail: [email protected]

Minerals: the building blocks of rocks

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Definition of a Mineral:

 naturally occurring   inorganic solid   characteristic crystalline structure definite chemical composition 1) Water or coal is a mineral.

F or T Why?

How do we identify minerals?

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Physical properties:

  Color Luster   Hardness Crystal shape   Cleavage Specific gravity All shown mineral examples have the same hardness, crystal shape, , specific gravity, and cleavage pattern.

2) Are they the same mineral? 3) Why?

Physical Properties of Minerals

Which one is metallic mineral (left, right, or both) Which one looks heavier?

Metallic vs

Galena is an important ore of gold.

F or T How many cleavage plans of Galena?

Physical Properties of Minerals

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Hardness:

– How easy it is to scratch a mineral – Mohs Scale of Hardness • relative scale • consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

Mohs Scale of Hardness

Common objects: - Fingernail (2.5) - Glass (5.5) These mineral can be scratched by glass, but have no scratch when using finger nail. Which minerals could be ?

Physical Properties of Minerals

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Cleavage

– The way a mineral breaks – Cleavage: tendency of a mineral to break along planes of weakness •

Cleavage is described by:

– Number of planes – Angles between adjacent planes

Physical Properties of Minerals

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Cleavage (1 direction):

Example:

mica

Physical Properties of Minerals

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Cleavage (2 directions):

orthoclase amphibole

Physical Properties of Minerals

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Cleavage (3 directions):

halite calcite

Physical Properties of Minerals

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Cleavage (4 directions):

fluorite

Physical Properties of Minerals

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Specific gravity:

–

weight

of a mineral divided by

volume

equal volume of water of an – metallic minerals tend to have higher gravity than non-metallic minerals specific Galena SG=7.5

Quartz SG=2.67

Physical Properties of Minerals

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Other properties:

– reaction with hydrochloric acid (calcite fizzes) – taste ( halite tastes salty) – feel and impression (talc feels soapy, graphite feels greasy) – magnetism (magnetite attracts a magnet)

Good places to get information on minerals

• Photos of minerals and short explanations: • http://mineral.galleries.com/Minerals/By_Name.html

• Everything you might want to know about a mineral and then some. Check out the nice crystallographic animations!

• http://webmineral.com/ • Handy guide to mineral identification: • http://www.minsocam.org/MSA/K12/properties/minpropind ex.html

• Common minerals and their uses: • http://www.mii.org/commonminerals.html