Minerals and Their Properties

Study Notes

Minerals and Their Characteristics

Minerals are the building blocks of rocks.
They are composed of one or more chemical elements.
Minerals have a definite chemical composition, which can be represented by a chemical formula.
Atoms in minerals are arranged in an orderly, repeating pattern forming a crystalline structure.
Minerals are naturally occurring, inorganic solids with a definite volume and rigid shape.

Different Properties of Minerals

Minerals are distinguished based on different physical and chemical properties.
Physical properties, like color, streak, hardness, cleavage, and crystalline structure, can be readily observed and used for identification.
Chemical properties, however, aren't as easily determined.

Properties of Minerals: Specific Details

Color: A mineral's color can vary depending on the surface.
Streak: The color of a mineral in powdered form.
Hardness: A mineral's resistance to being scratched. The Mohs scale of hardness rates minerals from 1 (softest - talc) to 10 (hardest - diamond).
- 10 - Diamond
- 9 - Corundum
- 8 - Topaz
- 7 - Quartz
- 6 - Orthoclase
- 5 - Apatite
- 4 - Fluorite
- 3 - Calcite
- 2 - Gypsum
- 1- Talc
Cleavage: A mineral's resistance to being broken and its fracture.
Crystalline structure/habit: How the crystals grow and look.
Diaphaneity/Transparency: The ability of light to pass through a mineral.
Luster: How light is reflected off a mineral's surface.
Tenacity: How a mineral reacts to stress (e.g., brittle, malleable, ductile, flexible).
- Brittleness: mineral turns to powder
- Malleability: mineral flattens under pressure
- Ductility: mineral can be stretched into wire
- Flexible but inelastic: mineral bends but returns to original shape
- Flexible and elastic: mineral bends and stays in the new shape
- Sectility: Ability of minerals to be sliced by a knife

Specific Mineral Examples

Diamond: Hardest naturally occurring mineral; made of carbon molecules; excellent insulator.
- Color: white to blue, pale yellow to colorless
- Formed at high pressure; Not reactive to strong acids and bases .
Calcite: Common non-silicate rock-forming mineral.
- Calcium Carbonate (CaCO3)
- Brittle
- Found in sedimentary and hydrothermal environments.
- Color: generally white to colorless
- Reacts with weak acids like vinegar and vigorously with diluted hydrochloric acid
Quartz: Complex silicate (SiO2).
- Often referred to as a framework silicate.
- Found in different kinds of rocks.
- Color: variable, but usually clear, white, milky white, purple, pink, brown
- Inert and unreactive at room temperature; resistant to chemicals and heat.
Biotite: Member of the sheet silicates.
- Color: dark brown to greenish brown to blackish brown.
- Flexible but breakable.
- Needs optical, chemical, or X-ray analysis; Not very resistant to weathering.
Gypsum: Most common sulfate mineral.
- Water-soluble sediment.
- Color: clear, colorless, white, gray
- Limited durability due to hardness; Soluble in hydrochloric acid.
Talc: Softest mineral; has a soapy or greasy texture.
- Color: white, colorless, grey, or green
- Resistant to heat, electricity, and chemicals; Not flammable.
Olivine: Member of the silicate family; susceptible to weathering.
- Almost as hard as quartz
- Color: from translucent to olivine green to glassy.
- Important mineral in Earth's mantle; crystallizes at high temperatures; Very resistant to chemicals.
Chlorite: Sheet silicate, similar to biotite.
- Generally various shades of green; slight greasy texture; produces a phantomed crystal.
Garnet: Commonly found in different kinds of rocks.
- Types: Calcium garnets (low hardness, green); Manganese garnets (higher hardness, red)
- Color varies from red to reddish; Most are translucent.