At least one: rarity. A second may be desire by humans to own them and wear them as adornments.
Blue sapphires are natural gemstones they are not made. Which is what makes them a precious gem stone.
Mainly minerals and precious and semi-precious gemstones.
Because they're beautiful and/or rare.
Two main types; precious stones and non precious stones.
Both are considered precious gemstones.
It depends. All gemstones other than pearls and opals are crystals, but most crystals are not gemstones.
Peter C. Keller has written: 'Gemstones of east Africa' -- subject(s): Precious stones 'Gemstones and their origins' -- subject(s): Precious stones
1 pound of anything except some gemstones and precious metals = 16 ounces of it 5 pound of anything except some gemstones and precious metals = 80 ounces of it
When describing them, you could call them precious gems or gemstones.
All precious stones come from rocks, but pearls are formed by oysters. Synthetic gemstones are made in factories.
The precious and the semi-precious jewels and the gemstones were the major goods often brought to Persia by means of the Silk Route.
Fluorite is not particularly durable nor particularly rare as most precious gemstones are.