About Quartz Crystal

Quartz is the second most abundant mineral in the Earth's continental crust (after feldspar). There are many different varieties of quartz, several of which are semi-precious gemstones. Especially in Europe and the Middle East, varieties of quartz have been since antiquity the most commonly used materials for the making of jewelry and hardstone carving.

Major Varieties of Quartz
Chalcedony
Cryptocrystalline quartz and moganite mixture. The term is generally only used for white or lightly colored material. Otherwise more specific names are used.
Agate
Multi-colored, banded chalcedony, semi-translucent to translucent
Onyx
Agate where the bands are straight, parallel and consistent in size.
Jasper
Opaque cryptocrystalline quartz, typically red to brown
Aventurine
Translucent chalcedony with small inclusions (usually mica) that shimmer.
Tiger's Eye
Fibrous gold to red-brown coloured quartz, exhibiting chatoyancy.
Rock crystal
Clear, colorless
Amethyst
Purple, transparent
Citrine
Yellow to reddish orange to brown, greenish yellow
Prasiolite
Mint green, transparent
Rose quartz
Pink, translucent, may display diasterism
Rutilated quartz
Contains acicular (needles) inclusions of rutile
Milk quartz
White, translucent to opaque, may display diasterism
Smoky quartz
Brown to grey, opaque
Carnelian
Reddish orange chalcedony, translucent

Source: Wikipedia