What is this?

• Are you sure this is a rock? What else could it be?

• What tests could you do to determine the type of rock you just picked up?

3-1 Properties of Minerals

What is a Mineral?Identifying Minerals

What is a mineral?

• To be a mineral a substance must have the following characteristics:

• Inorganic• Solid• Naturally Occurring• Has a Crystal structure • Definite chemical

composition

Inorganic

• A mineral cannot form from materials that were once part of living things.

Solid

• Minerals are solid, which means they have a definite volume and shape.

• The particles in a solid are tightly packed together so they cannot move.

Minerals are solid.

Naturally Occurring

• Formed by processes in nature

Crystal Structure

• The particles in a mineral form a repeating pattern

Definite Chemical Composition

• A mineral always contains certain elements in certain amounts.

•Example: SiO2 is Quartz

Color

• Color can be used to identify a few minerals

• This is not the best test because many minerals are the same color.

Streak

• The streak test identifies the color of the powder of a mineral. While a mineral’s color may change its streak will not.

Luster

• Luster refers to the way that light reflects off of the mineral’s surface.

Density

• Density is defined as “Mass per unit volume.”

• In other words, how many particles are in a certain area.

Hardness• Hardness is a

minerals characteristic of being able to scratch softer minerals and be scratched by harder minerals

Moh’s Hardness Scale

• Moh’s Hardness scale

• Ranks minerals from softest (1) to hardest (10)

Crystal Systems

• Each mineral has a particular crystal structure

• Example Cubic, hexogonal

Crystal Structure

Cleavage and Fracture

• Minerals with cleavage break along flat plains. While minerals with fracture break more jaggedly but the break can still have a pattern.

• For example: the image above has fracture in a sea-shell shape.

Fracture

Cleavage

Special Properties• Some minerals can

be identified by special properties they have.

• For example: Magnetite is magnetic and Scheelite glows in the dark (fluorescence)