Minerals:
Mineral - a naturally occurring, inorganic, solid substance that can exist either as a
compound or as a pure element.
Mineralogy - the study of minerals; there are over 2000 known minerals but only 250
are considered to be common.
Mineral Characteristics:
1. Color - the most obvious but also the most unreliable property when used
alone.
2. Streak - the color of the powered mineral on a porcelain streak plate.
3. Hardness - a mineral’s resistance to being scratched.
Moh’s Scale of Hardness
Field Scale
1 talc
4 fluorite
6 feldspar
8 topaz
2.5 fingernail
2 gypsum 5 apatite
7 quartz
9 corundum
3 penny
3 calcite
10 diamond
5 nail
5.5 glass
6 streak plate
4. Luster - the way a mineral’s surface reflects light.
Metallic - the look of metal (silver)
Nonmetallic:
Vitreous - the look of glass (quartz)
Pearly - the look of a p[earl (feldspar)
Dull - little or no reflection (chalk)
5. Cleavage - the breaking of a mineral with flat, smooth sides.
Basal
2-way
Cubic
Rhomboidal
4-way
Fracture
6. Specific Gravity - the weight of a mineral compared to the weight of an equal
volume of water.
7. Crystal Form - under favorable conditions, minerals will grow into crystals.
Their molecules arrange themselves into definite geometric patterns.
There are six different groups that minerals belong to.
8. Special Properties - possessed by only a few minerals.
Acid Test - react to HCl (calcite CaCO3)
Taste - salty (halite NaCl)
Odor - rotten egg (sulfur S)
Magnetism - attracted to a magnet (magnetite)
Fluorescence - glows in the presence of UV light (franklinite)
Most Common Elements - oxygen & silicon
Most Common Mineral Group - silicates
Most Common Minerals - feldspar & quartz (weather into clay and sand)
Element / Minerals - gold, silver, sulfur, copper, platinum, carbon (diamond & graphite)
Gem Requirements :
1. pretty
2. rare
3. hard