MINERALS

DEFINITION

• A mineral is:• Naturally occurring substance

• Inorganic (not living)

• Solid

• Has a definite (specific) crystal structure

• Made of a specific chemical compound

CLASSIFICATION OF MINERALS

• How minerals are identified is called, classification.

• Using the following tests, the exact mineral can be determined

COLOR

• Color – this is NOT a good clue to the identity of a mineral because many minerals are found in several colors and many minerals have extra chemicals in them that give them an unexpected color. Weathering may also change the color of the mineral.

• Example: quartz comes in various colors: rose, milky, clear

LUSTER

• Luster - the way a mineral reflects light. Minerals can be described as metallic, pearly, glassy, silky, greasy, brilliant, or dull.

• Example: diamonds are brilliant. Talc has a greasy luster, quartz has a glassy luster, and gypsum has a pearly luster. Pyrite or fool's gold, as it is sometimes called, has a metallic luster.

STREAK

• Streak - the color of the streak made by rubbing a mineral across a hard, rough surface like a bathroom tile which is known as the streak test

• Example: is pyrite which is a brassy, yellow color. However, it makes a greenish, black streak when rubbed across a rough surface. You will need a field guide to rocks and minerals to tell you what color streak a mineral makes.

CLEAVAGE AND FRACTURE

• Cleavage & Fracture are when certain minerals break in a definite way.

• Cleavage = square or flat sides

• Fracture = irregular breaks

• Example: Galena cleaves into little cubes. Mica cleaves into thin sheets. Calcite cleaves into slanting bricks. Feldspar breaks into little steps. Quartz cleaves into irregular chunks.

HARDNESS

• Hardness is measured by seeing how easy it is to scratch a mineral which is known as the scratch test

• Example: talc, the softest mineral known, can be scratched with a fingernail. Diamond, the hardest mineral, can scratch all the other minerals but cannot be scratched by them. A German mineralogist, Friedrich Mohs, developed a standard scale of hardness in 1822. His scale is so easy to use that it is still in use today.

MOHS HARDNESS SCALE

MineralExample Description

1 Talc Fingernail scratches it easily.

2 Gypsum Fingernail scratches it.

3 Calcite Copper penny scratches it.

4 Fluorite Steel knife scratches it easily.

5 Apatite Steel knife scratches it.

6 Feldspar Steel knife does not scratch it easily, but scratches glass.

7 Quartz Hardest common mineral. It scratches steel and glass easily.

8 Topaz Harder than any common mineral.

9 Corundum It scratches Topaz.

10 Diamond It is the hardest of all minerals.

SPECIFIC GRAVITY/DENSITY

• Specific gravity of a mineral is its relative weight compared to the weight of an equal volume of water. It determines the density of the mineral.

• Example: Two minerals may be the same size, but their weight may be very different. Water has a specific gravity of 1. If a mineral has a specific gravity less than 3, it is considered a "light" mineral, between 3 and 5 - "average", and more than 5 - "heavy". Minerals with a metallic luster are usually "heavy".

CRYSTAL STRUCTURE

• Specific and regular crystal patterns

OTHER PROPERTIES

• Acid Test – whether it reacts to acid

• Magnetism – whether there is a push or pull against other metals

PROCESSES THAT RESULT IN THE FORMATION OF MINERALS

• The processes that result in the formation of minerals are

• The cooling and crystallization from magma/lava• Bigger crystals form when it cools slowly

• Evaporation of liquid from a solution

MAJOR GROUPS OF MINERALS

• The two major groups of minerals is silicate and

non-silicate minerals.

• Silicate minerals contain Silicate groupings. Silicate minerals are minerals that have a combination of silicon and oxygen.

• Non-silicate minerals do not contain silicate. Non-silicate minerals are minerals that do not have a combination of silicon and oxygen.

SULFIDES AND SULFATES

• Sulfate is a combination of oxygen and sulfur whereas sulfide is the negative ion of sulfur alone. Both are negative ions.

Both sulfur and oxygen are "hungry" for electrons. When they make a chemical bond it is to gain a share of electrons to put them into a more stable electron mode (or configuration).

The suffix '-ate' in chemistry indicates that there is oxygen present whereas '-ide' tells us that only the element alone is present in forming the ion.

USES OF MINERALS

• Gems – jewelry

• Metals – strength

• Ores – mined for a profit

• Smelt – the melting of minerals

MINING

• Open Pit Mining

• Shaft Mining

• Strip Mining

ENVIRONMENTAL IMPACT

• Waste materials

• Depletion of resources

• Damage to surface or cause sink holes in caves