Minerals

Most minerals occur as crystals when conditions are suitable. In most cases these crystals are too small to be used to identify the minerals so other tests are needed.

Luster Luster refers to the way in which the mineral reflects light. It may be referred to as metallic (like a metal) or non-metallic.

Color Color is the easiest property to see and not always the most useful. It is important to describe the color of a freshly broken or scratched surface

Streak Often the color of a mineral is different when it is in a single lump or when it is powdered. The color of the powdered form is called the streak. The most common method of getting this powdered mineral is to rub the sample on the unglazed surface of a ceramic tile.

Streak Test

In larger samples, the shape of the crystal can be important in helping to identify the mineral

Acid (fizz) Test Effervescence (the Fizz test): Non-silicate carbonate minerals (CaCO3) will generally react when exposed to hydrochloric acid (HCl). Carbon dioxide (CO2) is released and the mineral or rock literally "fizzes."

Cleavage- or How a Mineral Breaks When a mineral breaks it can be in an irregular manner - fracture Or it can split along well defined surfaces - cleavage. Cleavage is used to distinguish between minerals when the other properties are similar.

Specific Gravity (Heft) Specific gravity is a measure of the density of a mineral. Pick it up? Is it heavier than an other mineral that look the same?

Hardness The hardness of a mineral is determined by what it will scratch and what scratches it. In 1822, the Austrian mineralogist Moh devised a scale from 1 - 10 using 10 common minerals: 1 - Talc (softest) 6 - Orthoclase 2 - Gypsum 7 - Quartz 3 - Calcite 8 - Topaz 4 - Fluorite 9 - Corundum 5 - Apatite 10 - Diamond (hardest)

We do not always have this set of minerals but the following are usually readily available: Fingernail 2.5 Copper Coin 3.5 Pocket Knife 5.5 Scratches Glass >6