Identifying Minerals

There are seven ways to identify a mineral.

1. Color 2. Luster 3. Streak 4. Cleavage and Fracture 5. Hardness 6. Density 7. Special properties

Color

The same mineral can come in a variety of colors.

For example, in its purest state quartz is clear. But some types and varieties can con contain impurities and can be of a variety of colors.

Other factors can change the appearance of minerals.

The mineral pyrite, often called fool’s gold, normally has golden brown color. But if it is exposed to air and water for a long period of time, it can turn brown or black.

Color is usually not the best way to identify a mineral.

Luster

The way a surface reflects light is called luster.

When we describe an object as dull or shiny, we describe its luster.

Minerals can have a metallic, sub metallic or nonmetallic luster.

If a mineral is shiny, it has a metallic luster.

If a mineral is dull, its luster is either sub metallic or nonmetallic.

Streak

The color of a mineral in powered form is called the mineral’s streak.

A mineral’s streak can be found by rubbing the mineral against a piece of unglazed porcelain called a streak plate.

The mark left on the plate is the streak.

The streak is a thin layer of powered mineral.

Streak is not affected by air or water.

Using streak is more reliable than using color in identifying a mineral.

Cleavage and fracture

Cleavage is the splitting of a mineral along smooth, flat surfaces.

Fracture is the manner in which a mineral breaks along either curved or irregular surfaces.

Hardness

A mineral’s resistance to being scratched is called hardness.

To determine the hardness of minerals, scientist use Mohs hardness scale.

The greater a mineral’s resistance to being scratched is, the higher the mineral’s rating.

Density

Is the ratio of mass of a substance to the volume of the substance.

Density= Mass/volume

The ratio of an object’s density to the density of water is called Specific gravity.

Special properties

1. Fluorescence 2. Magnetism 3. Chemical reaction 4. Taste 5. Optical properties 6. Radioactivity

Mohs hardness scale