Chapter 5

1. Inorganic
2. Occurs naturally
3. Crystalline solid
4. Consistent chemical composition Gypsum
Fluorite

Salt?
Sugar?
Ice?
Charcoal?
Rock?

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Scientists have identified 3,000 minerals
Of those minerals, there are 20 common
All minerals are divided into 2 main groups: Silicate and Nonsilicate Minerals
Silicates
Nonsilicates

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Must have Silicon and Oxygen
Usually has additional elements like Ca, Na, K,
Fe, or Mg
96% of Earth’s crust
Quartz and feldspar make up more than 50% of the crust

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Do not contain silicon and oxygen
Make up 4% of Earth’s crust
There are 6 major classes

Mineralogists identify minerals based on a number of specific physical properties:
 Color
 Streak
 Luster
 Cleavage and Fracture
 Hardness
 Crystal Shape
 Density

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Easy to observe
Unreliable
Trace amounts of elements can change color
Weathering can change color
The same mineral can come in different colors.
Rubies are cut from corundum with traces of Chromium (Cr)
Sapphires are cut from corundum with traces of Cobalt (Co)

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Color of the mineral in the powder form
More reliable than color
Use a
Minerals that are harder than the streak plate will leave no streak because it is too hard to rub off on the plate

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Light reflected from the mineral’s surface
: waxy, pearly, glassy, dull/earthy, or vitrious/brilliant

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is the tendency of a mineral to split along specific planes of weakness to form smooth, flat surfaces
Cleavage in three directions. Example: CALCITE

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is when the mineral does not split along cleavage planes
Fracture can be irregular, fibrous, or conchoidal

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A measure of the ability of a mineral to resist scratching
Hardness relates to the strength of bonds between the minerals atoms (Ex:
Diamond vs.
Graphite)

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To determine an unknown mineral’s hardness, you need to scratch it against a mineral of known hardness

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TETRAGONAL, ORTHORHOMBIC,
HEXAGONAL, TRICLINIC, MONOCLINIC,
ISOMETRIC

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Ratio of mass to volume of a substance
Density = mass/volume
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Most minerals have a density between 2 and 3 g/cc
Lead
Density = 11.35 g/cc
Galena
Density = 7.6 g/cc

 Fluorescence – ability to glow under UV light
 Double Refraction – light is bent to produce a double image
 Magnetism
 Radioactivity