Diamond C

10

3.5

Brilliant

White

Colorless and varied

Hardest known substance; used in jewelry, as an abrasive, in cutting instruments

Topaz Al₂SiO₄[F,OH]₂

8

3.5–3.6

Glassy

White

Straw yellow, pink, bluish, greenish

Used in jewelry, as a birthstone

Quartz SiO₂

7

2.6

Glassy, greasy

White

Colorless, white; any color when not pure

The second most abundant mineral; many varieties gems (amethyst, cat's eye, bloodstone, agate, jasper, onyx); used in making glass

Feldspar [K,Na,Ca]AlSi₃O₈

6

2.6

Glassy

Colorless, white

Colorless, white, various colors

As a family, the most abundant of all minerals; makes up more than 60 percent of Earth's crust

Fluorite CaF₂

4

3.0–3.3

Glassy

Colorless

Purple, light green, yellow, bluish green, other colors

Some types fluorescent (glow when exposed to UV light); used in making steel

Dolomite CaMg(CO₃)₂

3.5–4

2.8

Glassy or pearly

White

Colorless, white, pinkish, or light tints

Used in making concrete and cement; fizzes slowly in dilute hydrochloric acid

Calcite CaCO₃

3

2.7

Glassy

White to grayish

Colorless, white, pale tints

Easily scratched; bubbles in dilute hydrochloric acid

Halite NaCl

2.5

2.1–2.6

Glassy

White

Colorless or white

Occurs as perfect cubic crystals; has salty taste

Gypsum CaSO₄•2H₂O

2

2.3

Glassy, pearly, silky

White

Colorless, white, light tints

Very soft; used in manufacture of plaster of Paris; form known as alabaster used for statues

Sulfur S

2

2.0–2.1

Resinous to greasy

White

Yellowish to yellowish brown

Used in making many medicines, in production of sulfuric acid, and in vulcanizing rubber

Talc Mg₃Si₄O₁₀(OH)₂

1

2.7–2.8

Pearly to greasy

White

Gray, white, greenish

Very soft; used in talcum powder, found mostly in metamorphic rocks; also used in “soapstone”