- MINERALS:
A Mineral is a naturally occurring solid with a definite, orderly crystal structure and a defined chemical formula.
There are hundreds of minerals known. Several common minerals are listed on page 16 of the accompanying
Reference Tables.
An ore is a mineral used as a source of an economically important material. Examples: Hematite is an important ore of iron,
and galena is an importany ore of lead.
Several minerals are commercially useful in their natural form (or crushed):
- Halite (salt) can be used to melt ice on roads, or purified for use in foods.
- Graphite can be used as an industrial lubricant.
- Calcite can be used to make cement or concrete.
- Gypsum can be used in construction (of wallboard, for example).
- Biotite mica and Muscovite mica can both be used as an insulation (for pipes, etc.)
Quartz is the most abundant mineral in the Earth's crust. Sand is mostly ground-up quartz.
Many silicate minerals (made largely of strong lattices of silicon and oxygen atoms) are important components of rocks in the Earth's crust.
- Mineral hardness:
The hardness of a mineral is a measure of how easily it scratches other minerals. A harder mineral can always scratch a softer one.
Hardness is measured on a scale from 1 to 10, as follows:
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
| 6. Orthoclase feldspar
7. Quartz
8. Topaz
9. Corundum
10. Diamond
|
To remember the first letters of the names of the minerals in this sequence, say "The Girls Can Flirt
And Other Queer Things Can Do."
- Cleavage:
Many minerals form crystals that break apart along smooth planar surfaces that reflect light; they are said to show good cleavage.
Minerals that do not show good cleavage will often fracture along irregular surfaces.
Some minerals can occur both ways, depending on the temperature and pressure conditons under which they were formed.
- Streak:
If you scratch a mineral across an unglazed porcelain tile, it will often show a streak of powdery material.
The color of the streak can help identify the mineral. The streak color may be different from the appearance of the mineral itself.
|