Quartz

Quartz is one of the most common minerals in the Earth's continental crust. The most important distinction between types of quartz is that of macrocrystalline (individual crystals visible to the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals visible only under high magnification). Major varieties:

• Agate - banded chalcedony, translucent
• Amethyst - purple, transparent
• Aventurine - translucent chalcedony with small inclusions (usually mica) that shimmer
• Carnelian - reddish orange chalcedony, translucent
• Chalcedony - any cryptocrystalline quartz, although generally only used for white or lightly colored material
• Citrine - yellow to reddish orange, greenish yellow
• Jasper - opaque chalcedony, impure
• Milk Quartz (Snow Quartz) - white, translucent to opaque
• Morion - dark-brown, opaque
• Onyx - agate where the bands are straight, parallel and consistent in size
• Prasiolite - mint green, transparent
• Rock Crystal - clear, colorless
• Rose Quartz (Pink Quartz) - pink, translucent
• Smoky Quartz - gray or brown, transparent
• Tigereye - fibrous quartz, exhibiting chatoyancy