Minerals

A Mineral is a solid or single element (such as gold) or a compound of elements from the Earth's crust that has a definite chemical composition and crystal shape.

The characteristics and properties of these minerals can vary.

A Mineral can be identified by its properties that it can be tested for.

The Luster of a mineral describes the way a mineral reflects light. Minerals that reflect light like gold and silver are referred as having a metallic luster. All other minerals are referred to as having a nonmetallic luster. Quartz reflects light and therefore has a luster, but the luster is considered nonmetallic (luster not reflecting like a metal).

The Hardness of a mineral refers to how easily it can be scratched. Talc is considered the softest mineral and can be scratched by all other minerals. Diamond is considered the hardest mineral since no other mineral can scratch it. The Mohs Mineral Hardness rating is numbered 1 through 10 where Talc is a 1 and Diamond is a 10 on the hardness scale.

The Color of a mineral is not most reliable method in identifying a mineral. Many minerals have the same coloring, but a mineral's color can be used with other tests to identify the mineral.

Planar Cleaving (Cleavage) of a mineral is how easily it will split along a flat surface. Some minerals break apart naturally into flat sides. The direction of a flat side is called a plane. A mineral can contain one or more different Cleavage plane directions. A leaf would be considered having one plane direction and two sides. A cube contains three plane directions but six sides.

The Streak is the color of a mineral left behind when rubbed on a tile. The streak of most minerals is either colorless or the same color as the mineral. A few minerals have a streak different from the mineral's color. Pyrite (Fool's Gold) and Gold have a similar luster and color. When streaked, Pyrite produces a greenish black streak while Gold produces a gold streak.