Download Section 1.2: Identifying Minerals

 You can use different properties of minerals to help
identify them
 Color
 Luster
 Streak
 Cleavage & Fracture
 Hardness
 Density
 Other Special Properties
 Color
 Same mineral can exist in a variety of colors
 Pure quartz

 Yellow quartz
Black Onyx quartz
Rose quartz
Purple Amethyst
Smokey Brown
 Color
 Various amounts and types of impurities affect color
 Impurities like other minerals
 Exposure to other substances (air, water, etc.)
 Not usually the best way to identify a mineral
 Luster
 The way a surface reflects light
 “shiny or dull”
 Minerals Classified as
 1) metallic luster
 bright, “shiny”, reflective
gold
 2) sub-metallic luster
 dull, reflective
hematite
galena
 Luster
 3) nonmetallic luster (see Section 2 Figure 1)
 Vitreous
 Silky
 Resinous
 Waxy
 Pearly
 Earthy
 Streak
 The color of a mineral in its powdered form
 Found by rubbing the mineral against a streak plate
(unglazed porcelain)
 Not always the same color as the mineral sample
 Not affected by air
 More reliable than using color in identification
 Cleavage & Fracture
 The way a mineral breaks/fractures is determined by the
arrangement of its atoms
 Cleavage-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
 Hardness
 A minerals resistance to being scratched
 Mohs Hardness Scale uses 10 reference minerals for
comparison
 If the reference mineral scratches your unknown, the
reference mineral is harder than your unknown
 Density
 A 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)
 Special Properties (particular to a few types of minerals)
 Fluorescence
 Glow under ultraviolet light
 Magnetism
 Attract iron
 Chemical Reaction
 “Fizz” (gas released) when weak acid is added
 Taste
 Halite has salty taste
 Optical Properties
 Calcite and double image
 Radioactivity
 Radiation detected with a Geiger counter
 The Standard Deviants: Physical Properties for
Classifying Minerals
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