Unit: Earth Materials Minerals

Albite is a mineralbecause it meets 5 important conditions,as do....

almandine andalusitecrystals

apatite augite

azurite

I. There are over 3000 DIFFERENT minerals

identified in the earth’s crust.1. Few dozen are common (page 16 ESRT)

2. Same minerals found in most rocks.

3. Most minerals are SILICATES:

Oxygen MOST ABUNDANT element in crust

Silicon is usually found with oxygen in most minerals.

• 4.Rock-forming minerals

• a.Silicates make up the greatest number of minerals found in rocks

– feldspars are the most common type of silicate

– quartz is very common in many disguises

Salt River Cobbles

• b.Oxides contain elements, often metals, and oxygen

• c.Sulfides are usually metals and sulfur

• d.Calcium Carbonates include calcite

• e.Ferrous minerals contain iron (Fe)

Just a few forms of Quartz

A few silicates

5. New York State minerals

• Garnets-used as abrasives, found in metamorphic rock in Adirondacks

• Gypsum, found where ancient seas

dried up in central/western NY

• Halite and other salts, from deposits

left by evaporating seas

• Wollastonite, shown, an evaporite.

6. Gems are valued because of their beauty, crystal structure, rarity and durability.

Many gems are actually silicates that have a unique combination of impurities, creating color,and internal arrangement of atoms, giving them a particular luster, hardness and crystal structure.

Semi-precious gems, such as amethyst and tiger’s eye, are more common.

II. The 5 properties of all minerals

• The properties of minerals are due to the internal arrangement of molecules.

1. They are all solid.

2. Crystal Structure: or orderly internal pattern of units.

3. definite chemical composition: which means that their elements are always in the same ratio.

4. They are inorganic (do not come from living things or the remains of

living things).

5. They are natural, not anthropogenic.(not man-made)

III. Mineral Identification:tests to determine the mineral

1. Luster- the manner in which the mineral shines in reflected light.

a. Metallic luster; the mineral looks like a metal

b. Non-metallic luster; anything that does not look like a metal.

Ex. Pearly, earthy, dull, glassy

• 2. Specific gravity- compares the weight of the mineral in air to the weight of the mineral in water.

• Or, compares the density of the mineral to the density of water.

3. Hardness- a measure of the minerals resistance to being scratched.

Moh’s scale of hardness compares minerals to

each other. Talc is 1,

diamond is 10.

4. Cleavage vs. fracture- description of the mineral’s tendency to break along definite

angles and planes. • cleavage: clean break.

predictable angle and flat surfaces.

• Fracture: rough and unpredictable break.

5. Streak- the color of the powdered form of a mineral, obtained from dragging it along an

unglazed porcelain plate.

• Metallic minerals have colored streaks.

• Non-metallic tend to leave white or light.

• Hard minerals leave no streak.

6. Color- color is not always helpful

• One mineral may have many colors,(calcite)

• Many minerals may have the same color (white, grey, brown).

• Some are distinct:• (malachite, azurite)

7. Other specific tests/indicators such as: calcite (CaCO3) fizzes

even in weak acids

• Acid test: calcite fizzes in even weak HCl acid.

• And calcite shows refraction

• Iron rusts

• magnetism: • fluorescence

• Flame tests • Salty taste

8. Crystal shape: how the axes and faces meet (need equipment and knowledge to do this

properly)

• 6 basic systems:

Clockwise from top rightWolfenite, olivine, turquoise,labradorite, siderite, gypsum, pyrite, uranite

Clockwise from top rightcalcite, lapis lazuli, magnetiteferrous mineral, titanite, halite, hematite, polarized viewgypum