MINERAL PROPERTIES & Identification



MINERAL PROPERTIES & Identification

Over 4,000 minerals have been identified. Yet no

two are exactly alike.

HOW TO IDENTIFY MINERALS

Using: (physical properties)

Color – Can be used for identifying only a

few minerals.

Example: Mineral sulfur is always yellow.

Luster – Is the way light reflects from its

surface (“Shine”).

Two Types of Luster

1. Metallic – shiny, like metal

2. Nonmetallic – dull, earthy

Streak – Is the color of the powder left when a

mineral is rubbed against a hard rough surface.

Example: Mineral hematite makes red streak

Hardness – Is a mineral’s resistance to being

scratched.

[pic]

Moh's Hardness Scale – minerals 1-10 of increasing resistance to be scratched

1 softest – 10 hardest

[pic]

[pic]

Acid – carbonate

Hardness test: penny 3.5, nail 5.5, glass 6.5

Streak plate – color of powder

Magnet – test for iron and other magnetic minerals

Mineral Identification (cont.)

Density (Specific Gravity) – is the comparison of the density of a mineral to the density of water.

Water = 1 gm/cm³

Most minerals = 2.5-3.5 gm/cm³

Gold = 18 gm/cm³ silver, gold, galena (lead ore)

have high specific gravity

Cleavage or Fracture –

Is the way a mineral breaks or splits apart. Most minerals tend to break along smooth surfaces, if so the mineral has cleavage. If it shatters with jagged edges it is called fracture.

Diamond and gem cutters use cleavage planes to cut the faces in gems

Special properties

Carbonates give of gases when a weak acid is placed on them.

Example – calcite CaCO3

Acid Test – this is used for carbonate minerals.

Magnetic test – magnet sticks to the mineral

Magnetite (iron ore) “load stone”

Salty taste – cubic crystals of Halite (rock salt)

(do not ever taste minerals in lab)

geologist do this as a field test

Radioactive – give off charged particles (radiation)

Example: Uranium

Test with an instrument called a Geiger counter

Florescence – mineral glows under a U.V. light

(ultraviolet)

example: mineral fluorite and many others

Double refraction image – multiple images when viewed through clear crystal

Example: calcite

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