Same mineral, new outfit.
Types of, Quartz
SiO2Mohs 7Trigonal
All types of quartz are the same mineral, silicon dioxide, and they differ in crystal size, color, shape and what got trapped inside. Here they are sorted the way a mineralogist would: crystal size first, then color, inclusions, crystal habit and treatments.
What all quartz types have in common
All quartz types share one formula, SiO2, a hardness of 7 and a trigonal crystal structure. Quartz has a glassy luster, breaks with curved, shell-like fractures instead of clean cleavage, and has a specific gravity of 2.65. It is the second most common mineral in Earth's continental crust after feldspar, which helps explain why it comes in so many colors and shapes. The full data is on Mindat's quartz page.
Crystalline vs microcrystalline quartz
Crystalline quartz grows as visible crystals, while microcrystalline quartz is built from grains or fibers too small to see without a microscope. Points, clusters and geode linings are crystalline and look glassy. Agate, carnelian, onyx and jasper are on the microcrystalline side and look waxy or dull.
Quartz varieties by color
Quartz varieties by color come down to a few causes: traces of iron or aluminum, natural radiation, and microscopic inclusions. Each of these has its own field guide.
- Clear quartz: nearly pure silicon dioxide, with nothing inside to absorb light.
- Milky quartz: white from countless microscopic bubbles of fluid trapped during growth.
- Smoky quartz: brown to black from natural radiation acting on traces of aluminum.
- Amethyst: purple from traces of iron plus natural radiation.
- Citrine: yellow to orange. Natural citrine is uncommon, and most on the market is amethyst heated until it turns gold.
- Rose quartz: pink from microscopic fibers of a mineral related to dumortierite.
- Pink amethyst: pale pink to lavender quartz from geodes in Patagonia, Argentina.
- Prasiolite: green quartz, usually amethyst from certain deposits that was heated.
- Ametrine: purple and gold zones in one crystal, mostly from the Anahí mine in Bolivia.
Quartz with inclusions
Quartz with inclusions is quartz that grew around other minerals and sealed them inside. The host is still quartz, so hardness and care stay the same.
- Super seven: amethyst and smoky quartz with flecks and needles of goethite, lepidocrocite, rutile and cacoxenite, originally from Espírito Santo, Brazil.
- Lepidocrocite quartz: clear quartz with red to orange flakes of iron oxide minerals.
- Lithium quartz: quartz clouded lilac or gray by fine mineral inclusions, sold under a trade name that points to lithium.
- Tangerine quartz: quartz coated or stained orange by iron oxide.
- Rutilated and tourmalinated quartz: golden rutile needles or black tourmaline rods frozen inside.
- Lodolite, or garden quartz: quartz filled with chlorite and other minerals that look like moss or tiny landscapes.
- Phantom quartz: the outline of an earlier crystal, traced inside by a thin film of dust or another mineral.
Quartz crystal habits
Quartz crystal habits describe the shape a crystal grew into, which has nothing to do with its color. One locality can produce several.
- Spirit quartz: larger crystals coated in tiny secondary points, from South Africa, often amethyst colored.
- Herkimer diamonds: short, very clear, double-terminated crystals from Herkimer County, New York.
- Scepters: a fat crystal cap grown on the end of a thinner stem.
- Skeletal or elestial quartz: stepped, etched crystals with many small tips, often smoky.
- Clusters and druzy: many crystals sharing one base, or a sugary crust of tiny ones.
Treated quartz types
Treated quartz types are real quartz changed by people after mining. Aura quartz is clear quartz coated in a vacuum chamber with a thin film of metals such as titanium, gold or indium, which gives the rainbow sheen (how aura quartz is made). Most bright citrine is heated amethyst. Jet black smoky quartz is often clear quartz darkened by radiation in a lab, and hot pink or electric blue points are usually dyed. None of these are fake quartz, but the colors are not natural, and an honest label says so.
Types of Quartz FAQ
How do you tell if a rock is quartz?
You can tell a rock is quartz if it scratches glass, has a glassy luster and breaks with curved fractures instead of flat cleavage planes. Quartz crystals are six-sided and usually end in a point.
What is green quartz called?
Green quartz is called prasiolite when it is transparent, and most prasiolite is heat-treated amethyst. Green aventurine is a quartz rock colored by green mica, and chrysoprase is chalcedony colored by nickel.
Is agate a type of quartz?
Agate is a type of quartz: banded chalcedony made of microscopic quartz fibers, with the same SiO2 formula and nearly the same hardness.
Is aura quartz natural?
Aura quartz is natural quartz with an artificial coating: the rainbow is a metal film bonded in a lab, and it can wear off with scratches.