Section 1.2: Identifying Minerals

You can use different properties of minerals to help identify themColorLusterStreakCleavage & FractureHardnessDensityOther Special Properties

Section 1.2: Identifying Minerals

ColorSame mineral can exist in a variety of colors

Pure quartz Black Onyx quartz

Rose quartz Purple Amethyst

Yellow quartz Smokey Brown

Section 1.2: Identifying Minerals

ColorVarious amounts and types of impurities affect

colorImpurities like other minerals

Exposure to other substances (air, water, etc.)

Not usually the best way to identify a mineral

Section 1.2: Identifying Minerals

LusterThe way a surface reflects light“shiny or dull”Minerals Classified as

1) metallic lusterbright, “shiny”, reflective

gold galena

2) sub-metallic lusterdull, reflective

hematite

Section 1.2: Identifying Minerals

Luster3) nonmetallic luster (see Section 2 Figure 1)

VitreousSilkyResinousWaxyPearlyEarthy

Section 1.2: Identifying Minerals

StreakThe color of a mineral in its powdered formFound by rubbing the mineral against a streak

plate (unglazed porcelain)Not always the same color as the mineral

sampleNot affected by airMore reliable than using color in identification

Section 1.2: Identifying Minerals

Cleavage & FractureThe way a mineral breaks/fractures is

determined by the arrangement of its atomsCleavage-the tendency of some minerals

to break along smooth, flat surfaces

Fracture-the tendency of some minerals to break unevenly along curved or irregular surfaces

Section 1.2: Identifying Minerals

HardnessA minerals resistance to being scratchedMohs Hardness Scale uses 10 reference

minerals for comparisonIf the reference mineral scratches your

unknown, the reference mineral is harder than your unknown

Section 1.2: Identifying Minerals

Mohs Hardness Scale

DensityA measure of how much matter is present in a

given space (D = m/V)Usually measured in g/cm3 (for solids)Specific Gravity – comparison of object’s

density to that of water (which is 1 g/cm3)

Section 1.2: Identifying Minerals

Special Properties (particular to a few types of minerals)Fluorescence

Glow under ultraviolet lightMagnetism

Attract ironChemical Reaction

“Fizz” (gas released) when weak acid is addedTaste

Halite has salty tasteOptical Properties

Calcite and double imageRadioactivity

Radiation detected with a Geiger counter

Section 1.2: Identifying Minerals

The Standard Deviants: Physical Properties for Classifying Minerals

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Section 1.2: Identifying Minerals