Quartz
Silicate · SiO₂ · also: Rock crystal
Quartz is the most common mineral in the Earth’s crust, a hard, glassy silicon dioxide that forms six-sided crystals in almost every colour.
What is quartz?
Quartz is crystalline silicon dioxide and one of the most abundant minerals on Earth. It grows as six-sided prisms capped by pyramid-like points, and its many coloured varieties (amethyst, citrine, rose and smoky quartz) are all the same mineral with trace impurities or natural irradiation. Because it is hard, chemically stable and widespread, quartz turns up in nearly every rock type and is a first mineral most collectors learn.
Properties
- Chemical formula
- SiO₂
- Category
- Silicate
- Hardness (Mohs)
- 7
- Crystal system
- Trigonal
- Lustre
- Vitreous (glassy)
- Streak
- White
- Colour
- Colourless, white, purple, pink, grey, yellow, brown
- Cleavage / fracture
- None; conchoidal fracture
How to identify quartz
- →Hardness of 7: it scratches glass and steel easily and cannot be scratched by a knife.
- →No cleavage; broken surfaces are curved and shell-like (conchoidal fracture).
- →Glassy lustre and often transparent to translucent.
- →Six-sided prismatic crystals ending in a point are a giveaway when present.
Where quartz is found
Quartz is found worldwide, in igneous, metamorphic and sedimentary rocks and lining countless veins and geodes. Fine crystals come from Brazil, Arkansas (USA), the Alps and Madagascar, but you can find quartz almost anywhere there are rocks.
Quartz finds on minShelf
Real specimens catalogued by collectors.
Think you've found quartz?
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