Minerals

Rock – an aggregate of minerals (mixture of minerals).

Mineral – naturally occurring, inorganic, crystalline solids, with a definite chemical composition.

All minerals are rocks, but not all rocks are minerals!

Minerals vs. Rocks

Granite (rock)

mixture of:

Feldspar(mineral)

Biotite(mineral)

Quartz(mineral)

1. Crystal Form External expression of a

mineral’s internal orderly arrangement of atoms.

Size of the crystal is based on time & available space.

Properties of Minerals

Crystal Shapes:

Cubic Hexagonal

Tetragonal

Orthorhombic

Monoclinic

Triclinic

2. Luster Appearance /quality of light

reflected from the surface of a mineral.

Metallic vs. Nonmetallic.

Properties of Minerals

Choosing the Luster:Luster

Metallic

Shiny like a metal?

Nonmetallic

Vitreous(glassy)

Yes No

What kind of nonmetallic?

Earthy

Resinous

SilkyPearly

3. Color Outer appearance. Unreliable property. A mineral may have

several color varieties.

Properties of Minerals

4. Streak Color of the mineral in a

powdered form. Obtained by rubbing the

mineral across a streak plate.

Properties of Minerals

5. Hardness Resistance to abrasion or

scratching.

Properties of Minerals

1. Talc2. Gypsum3. Calcite4. Fluorite5. Apatite6. Feldspar7. Quartz8. Topaz9. Corundum10.Diamond

Softest

Hardest

Mohs’ Scale

How to test a mineral’s hardness

1. Start by moving an unknown sample across a sample with a hardness of 1.

2. If the unknown scratches the known sample, then it is harder….so keep testing the others until it doesn’t scratch it.

3. If it doesn’t scratch it, then it is softer than the known sample so it is lower on the scale.

4. If they scratch each other, they are the same hardness.

6. Cleavage Tendency for a mineral to

break along planes of weak bonding.

Smooth surfaces. Not to be confused with

crystals.

Properties of Minerals

7. Fracture Opposite of cleavage. Conchoidal fracture = curved

edges. Fibrous fracture =

splinters/fibers.

Properties of Minerals

8. Specific Gravity Comparison between the

weight of a mineral to the weight of an equal volume of water.

Comparison of densities. Written as the number of times

heavier/lighter than water.

Properties of Minerals

9. Other Properties Taste Elasticity Malleability Texture Magnetism Double Refraction Reaction to acids (HCl)

Properties of Minerals

8 elements make up 98% of the Earth’s crust (by weight).OSiAlFeCaNaKMg

Mineral Groups

Silicate GroupMinerals made of O and Si. ¾ of the minerals in the continental crust are

silicates. Silicon-oxygen tetrahedron (1 silicon to 4

oxygen) then bonded to another element(s). EXAMPLES:

Quartz, Feldspars, Micas

Mineral Groups

Carbonates GroupMinerals made of CO3 bonded with other

elements.EXAMPLES:

Calcite & Dolomite

Halides GroupMinerals made with members of the halogen

family.Formed through evaporation.EXAMPLES:

Halite & Fluorite

Mineral Groups

Sulfates GroupMinerals made of SO4 bonded with other

elements.EXAMPLES:

Gypsum

Oxides GroupMinerals made with Oxygen bonded with other

elements.EXAMPLES:

Hematite & Ice

Mineral Groups

Native Elements GroupMinerals that are pure elements (usually

metals).EXAMPLES:

Copper, Diamond, Graphite

Sulfides GroupMinerals made with Sulfur bonded with other

elements.EXAMPLES:

Pyrite

Mineral Groups

Ores – useful metallic minerals that are mined at a profit.EXAMPLES: Hematite (Iron), Sphalerite (Zinc),

Galena (Lead), Cinnabar (Mercury).

Industrial rocks & minerals – useful nonmetallic minerals that are mined at a profit.EXAMPLES: Fluorite, Sulfur, Halite (salt)

The amount of a mineral in a deposit must be concentrated several times it’s crustal percentage to be considered profitable.

Mineral Resources

Gemstones – Crystal forms of minerals that posses beauty of such quality that command a price when cut & polished.

Precious gems – have beauty, durability, size, and rarity.DiamondEmerald (Beryl)Ruby (Corundum)Sapphire (Corundum)

Mineral Resources

Semiprecious gems – only have one or two of the qualities of precious gems.EXAMPLES: Amethyst , Topaz, Garnet, Zircon

Non-mineral gems – stones that have value, but are not minerals.EXAMPLES: Coral, Amber, Pearl

Precious Metals – metallic minerals that have high value.EXAMPLES: Gold, Silver, Platinum

Mineral Resources