2. Luster: The way a mineral reflects light may be classified as metallic (like metal); nonmetallic (like glass or dull); pearly (like a pearl); silky (like silk); greasy (like oil); waxy (like wax); earthy (like chalk); adamantine (brilliant like a diamond).

3. Streak: The color of the powder of a mineral. It differs from color which is the color the mineral appears to have. Scratch the mineral on an unglazed porcelain streak plate to obtain the streak. For some minerals, the streak color may be different from the mineral’s color. For example, hematite is black or steel-gray, but the streak is red-brown.

4. Hardness: The resistance a mineral offers to being scratched. Friedrich Mohs developed the Moh's Scale of Hardness, which rates minerals on a scale of 1 to 10, with 1 being the softest and 10 being the hardest.

5. Cleavage and Fracture: Cleavage describes how a mineral breaks along defined planes of weakness. Fracture is how a mineral breaks when it does not cleave.

6. Diaphaneity: This describes how light passes through a mineral. A transparent mineral allows light to pass through completely so objects can be seen through it. A translucent mineral allows some light through but objects can't be seen clearly. An opaque mineral blocks all light.

7. Crystal Form: The regular shape a mineral naturally forms when it crystallizes.