Minerals! Minerals!

What are minerals? Minerals are a category of substances found in the earth, formed on or below the surface.

Minerals must have the following traits: Minerals are solid (they have fixed shape and volume) diamond

Minerals are inorganic (not living material) not animal! not plant! emerald

Minerals are naturally occurring (not man-made) natural emerald natural ruby synthetic emerald synthetic ruby

Minerals are crystalline (form regular shaped chunks) uncut diamond natural quartz

Minerals have definite chemical composition (they are only made of certain elements)

Classifying minerals: (how to tell them apart) Density: how heavy it is for its size

Color: some minerals have more than one color, but same chemical composition The coloration of corundum (sapphires) is very different from that of calcite!

Streak: the color left by the mineral Some minerals leave unique streaks!

Luster: how it reflects light-- metallic, glassy, pearly, silky, earthy...

Cleavage/fracture: how easily it breaks, how it breaks (smooth, jagged, square...) Cleavage in four directions. Example: CALCITE

Other: reactivity, magnetic, conductivity, phosphorescence/glows cauliflower calcite

Hardness: how resistant it is to scratching talc flakes easily diamonds can’t be scratched!

Friedrick Mohs created a Hardness Scale: 10 is hardest, 1 is softest. He based it on 2 main scratch tests: Can be scratched by: Fingernail: soft, under 3 Copper: hardness of 3 Steel: hardness of 4-5 Can scratch: Glass: hardness of 6 Steel: hardness of 7-9 Anything: hardness of 10

Moh’s Hardness Scale