MINERALS

  1. Definition – A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition.

A.  Minerals are formed in nature.

B.  Minerals are inorganic.

C.  Minerals are solids.

D.  Minerals have a crystal shape.

E.  Minerals have an exact chemical composition.

  1. Mineral Formation

A.  Cooling of Magma

1.  Fast cooling of lava causes small crystals to form (basaltic).

2.  Slow cooling of magma causes large crystals to form (granitic).

B.  Evaporation of water containing large amounts of dissolved minerals.

1.  Fast evaporation causes small crystals to form.

2.  Slow evaporation causes large crystals to form.

  1. Types of Minerals

A.  Ore – a mineral from which usable amounts of metals and non-metals can be taken.

1.  Metal

a.  shiny

b.  malleable and ductile

c.  conducts electricity and heat

2.  Non-metal – does not have any of the qualities listed above.

B.  Gem – a mineral that is a non-metal, rare, beautiful and durable.

1.  Precious gems – rarest and most valuable.

a.  alexandrite

b.  diamond

c.  emeralds

d.  rubies

e.  sapphires

2.  Semi-precious gems – not as rare or valuable.

a.  amethysts

b.  zircons

c.  garnets

d.  turquoise

  1. Mineral Identification – Minerals are identified by their physical properties.

A.  Hardness is the mineral’s resistance to being scratched. Mohs Hardness Scale is used to determine hardness.

1.  talc 6. feldspar

2.  gypsum 7. quartz

3.  calcite 8. topaz

4.  fluorite 9. corundum

5.  apatite 10. diamond

B.  Color is the first property to be noted, but it is NOT reliable.

C.  Streak is the color of the powdered mineral. The streak color IS reliable.

D.  Luster is the way light is reflected from a mineral surface.

1.  Metallic luster looks like polished metal.

2.  Non-metallic luster does not look like metal.

E.  Cleavage or Fracture – the way mineral breaks.

1.  Cleavage is when the breakage is along smooth, flat planes.

2.  Fracture is the breakage along an irregular surface.

F.  Texture is the way a mineral feels.

G.  Special properties

1.  density

2.  odor

3.  magnetic

4.  taste

5.  reactivity to acid