Different Types of Quartz - The Ultimate Guide
The Most Popular Quartz Varieties
Quartz is one of the most abundant and versatile minerals on Earth.
Composed of silicon dioxide, quartz in its purest form is colourless and transparent to translucent. Trace impurities, structural variations, and different geological processes produce a wide range of colours, textures, and crystal shapes.
Many of the most well-known quartz varieties have been used and studied for thousands of years. Some types form well-defined crystals, while others grow as tightly intergrown masses with no external crystal shape.
This article explores some of the best-known and most easily recognisable varieties.
Agate
A translucent variety of chalcedony, best known for its distinctive banding. The bands form as layers of silica build up over time, often in cavities within volcanic rock. Agate occurs in a wide range of colours and has been used for jewellery, carvings, and decorative objects since ancient times.
Amethyst
A purple variety of quartz whose colour is caused by iron within the crystal structure. It commonly forms as crystals lining the inside of rock cavities. Exposure to heat and UV light can alter amethyst’s colour, sometimes turning it yellow or brown.
Aventurine
A variety of quartz identified by its plate-like mineral inclusions. These can give the stone a sparkly appearance, known as aventurescence. Aventurine most commonly occurs in green, but can also be found in orange, blue, and other colours.
Bloodstone
A dark green variety of chalcedony with red markings caused by iron oxide inclusions, usually hematite. When heated, the green base colour turns grey, and the red spots darken or turn black. Therefore, the colour of bloodstone is not enhanced through heat treatments.
Carnelian
A reddish to rich orange variety of chalcedony, typically translucent. Its colour comes from iron compounds within the quartz and can deepen when heated. The name Cornelian is an older spelling that's still sometimes used.
Chalcedony
A variety of microcrystalline quartz, meaning its crystals are too small to be seen with the naked eye. Chalcedony is typically white or pale grey in its purest form. Most coloured and patterned varieties are known by their own names, such as agate, bloodstone, jasper, and carnelian.
Chevron Amethyst
Alternating bands of purple amethyst and colourless or milky quartz. The distinctive V-shaped or zigzag pattern forms as crystal growth conditions change over time. Also known as banded amethyst, particularly in the UK.
Chrysoprase
A translucent apple-green variety of chalcedony whose colour is caused by traces of nickel. Prolonged exposure to high temperatures or sunlight can gradually dull the colour. High-grade material is relatively rare and valuable, so dyed agate and other green quartz varieties are sometimes mislabelled and sold as chrysoprase.
Citrine
A yellow to yellowish-brown variety of quartz. Natural citrine is relatively rare, so most commercial-grade citrine is produced by heating amethyst or smoky quartz, which changes the colour. Citrine rarely forms large, well-defined crystals. Many of the large 'citrine' geodes sold commercially are amethyst geodes that have been heated in industrial ovens.
Included Quartz
Included quartz refers to quartz that contains visible inclusions of other minerals trapped during crystal growth. Although some types, such as rutilated quartz, are known by their own names, many are grouped together under the broad term 'included quartz'.
Jasper
Jasper is an opaque, cryptocrystalline variety of chalcedony containing fine-grained inclusions of other minerals and materials. These prevent light from passing through the stone and are responsible for jasper's wide range of colours and patterns.
Milky Quartz
Also known as white quartz, snow quartz, and milk quartz. This white to greyish-white variety ranges from translucent to opaque. Its cloudy appearance is caused by microscopic fluid inclusions trapped during crystal growth. It often occurs in the same deposits as clear, colourless rock crystal.
Onyx
Traditionally defined as a banded variety of agate with straight, parallel layers. However, the name has been misused for centuries, and its exact definition is still debated. This has led to widespread confusion in the gemstone trade, particularly within the crystals and metaphysical/healing community.
Rose Quartz
A pink, translucent variety of quartz that occurs with a massive crystal habit. Pink quartz, which forms individual crystals, is far more scarce and fades when exposed to UV light.
Rock Crystal
The colourless, transparent variety of quartz. The name emerged during the late Middle Ages to distinguish natural quartz from newly produced colourless glass, which was commonly referred to as crystal or crystal glass. Rock crystal is not lead crystal, which is a man-made type of glass.
Sard
A translucent, light to dark brown variety of chalcedony. Until the Middle Ages, sard shared its name with carnelian. Gemstones showing bands of white chalcedony and sard are known as sardonyx.
Smoky Quartz
A translucent to transparent variety of quartz known for its large, well-formed crystals, often free from visible inclusions. It occurs in shades ranging from light brown to almost black. The colour is caused by natural radiation acting on trace elements within the crystal. The correct spelling is smoky, not smokey.
Tigers Eye
Tigers eye, also known as tiger eye, is a type of quartz with a rich golden-yellow colour caused by iron. Its silky, chatoyant appearance comes from parallel fibrous structures within the stone. It was long believed that quartz replaced the asbestos mineral crocidolite, but more recent studies have shown this to be incorrect.
Article Photos
The minerals at the top of our article are from our collection.
Pop-up photos: Queensland agate, Morrisonite (jasper), sardonyx: Courtesy of Captain Tenneal. Bloodstone, Chrysoprase: Courtesy of James St.John. Carnelian: Courtesy of Steve (singingstone 48 - Flickr). Citrine: Courtesy of Steve Blyskal. Milky quartz, sard (Natural History Museum - London), smoky quartz, amethyst geode: Stone Mania.
