The New Childrens Encyclopedia

ROCK AND MINERAL GUIDE

41

PRECIOUS STONES

O

Gemstones are divided into precious and

semiprecious stones based on value.

The four that qualify as precious are diamond,

emerald, sapphire, and ruby.

Agate: 7

Amethyst: 7

Jade: 6–7

Lapis lazuli: 3–5.5

Olivine: 6.5–7

Tormaline: 7 Zircon: 7.5

ORES

MOHS’ SCALE

1. Talc 2. Gypsum

SEMIPRECIOUS STONES

3. Calcite 4. Fluorite 5. Apatite 6. Feldspar 7. Quartz 8. Topaz 9. Corundum 10. Diamond

Diamond Emerald

Sapphire Ruby

Cobaltite (contains cobalt): 5.5

Gold: 2.5–3

Illmenite (contains

titanium): 5–6 Magnetite (contains iron): 5–6

Malachite

(contains copper):

3.5–4

Rhodonite (contains manganese): 5.5–6.5

Silver: 2.5–3

Sulfur: 1.5–2.5 on Mohs’ scale

softest hardest

EARTH

One way of telling the difference between similar-looking minerals is to test their hardness. This is measured by scratching

minerals against each other. A hard mineral can always scratch a softer one. The hardest mineral is diamond.