Quartz: Properties, Facts and Photos

Quartz is one of the most common and versatile minerals on Earth, found in everything from sand and glass to gemstones and electronic devices. Known for its wide range of colours and crystal forms, quartz occurs in many different varieties, including amethyst, citrine, jasper, and agate.

Contents 1. What is Quartz? 2. How Does Quartz Form? 3. Rock Crystal Clear Quartz 4. Article Pictures 5. Shop Quartz

What is Quartz?

Quartz, which is composed of silicon and oxygen, is the second most common mineral in Earth's crust after feldspar. It's found in almost every geological environment and is a component of virtually every rock type. It's also the primary constituent of most sand.

Because of its abundance and widespread distribution, quartz is the world's most diverse mineral in terms of varieties, colours, and forms. It occurs in sedimentary rocks as grains of sand and as crystals in igneous and metamorphic rocks.

Quartzite, which is composed almost completely of quartz, is produced through the metamorphism of sandstone.

Silicon dioxide, a chemical compound of silicon and oxygen, commonly occurs in nature as the mineral quartz. It exists in several crystalline forms and numerous cryptocrystalline forms.

Quartz is also known as silica.

The name 'quartz' is believed to come from the old German word 'quarz', which first appeared in 1530. In ancient Greece, quartz was known as 'krustallos', from 'kruos', meaning 'icy cold'. This may have come about because of the clarity of some quartz crystals.

Theophrastus, the ancient Greek philosopher and successor to Aristotle, believed colourless quartz crystals were a unique type of ice that wouldn't melt.

How Does Quartz Form?

Quartz crystals grow when silica-rich fluids cool and crystallise, most commonly within cracks, cavities, and veins in rock.

These hot, water-based solutions move through rock deep underground and carry dissolved silica, the chemical compound that eventually crystallises to form quartz. As the fluids cool or experience changes in pressure or chemistry, they can no longer hold the same amount of dissolved silica. The silica then precipitates and crystallises.

The size and shape of a quartz crystal depend on the conditions under which it grows. Slow cooling and a steady supply of silica allow larger, well-formed crystals to form, whereas rapid changes in environmental conditions tend to produce smaller or more irregular growth.

Quartz crystals often form distinctive pointed terminations, but growth can be interrupted or altered if space becomes limited or conditions change. This is why quartz occurs in such a wide range of forms, from well-shaped individual crystals to dense, intergrown masses with no obvious external shape.

The classic six-sided prism with a pointed termination is the reason most people can recognise a quartz crystal.

Changes in growth conditions and the presence of other substances also affect clarity. These variations explain why some quartz is transparent, while other forms are translucent or opaque.

In some environments, silica crystallises so rapidly or in such tight spaces that individual crystals never grow. The silica then forms as microscopic, tightly intergrown crystals.

This type of quartz, known as chalcedony, includes varieties such as jasper and agate. Agate forms when layers of silica build up gradually, often producing distinctive banding. Impurities can introduce colour.

Jasper contains more impurities and other materials, which block light, make it opaque, and also produce a wide variety of colours. Other varieties of chalcedony, such as tiger’s eye, form when silica grows alongside or around other materials, creating fibrous or patterned structures.

Varieties of quartz like chrysoprase, amethyst, smoky quartz, and citrine, develop their colour due to geological conditions, including impurities and natural radiation.

Rock Crystal: Clear, Colourless Quartz

Rock crystal is an alternative name for colourless quartz. Quartz is colourless and transparent to translucent when free from impurities, hence the term 'crystal clear.'

Impurities can produce a wide variety of colours, ranging from milky white to brown so dark that it can appear almost black.

Quartz exists in many different varieties and occurs in two main forms: crystalline, which has visible crystals, and cryptocrystalline, where the crystals are too small to be seen with the naked eye.

Coloured varieties of quartz tend to be translucent rather than transparent, and most have their own name. 

Inclusions in quartz are relatively common. Quartz with inclusions is often referred to as included quartz. Rutile and tourmaline are two of the most common mineral inclusions.

The optical properties of quartz led to its extensive use in lenses and prisms. It was once widely used in electronic components but has now been replaced with a synthetic alternative.

As well as having electrical properties (piezoelectric), quartz is also resistant to heat. Being graded 7 on the Mohs scale makes it harder than many other natural minerals. It's therefore often used as an abrasive.

Despite its hardness, quartz is brittle, so it can break or shatter easily.

In geology, hardness and toughness are not the same. One refers to a mineral's resistance to being scratched by another, while the other refers to its resistance to being bent, cracked, chipped or broken.

Explore the many different varieties of quartz, including bloodstone, chrysoprase, rock crystal, jasper, and tigers eye, in this article in our blog: The Ultimate Guide to Quartz.

Article Pictures

The quartz in this article is from our collection.

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Quartzite, rutilated quartz, Jasper (from Vancouver): Courtesy of Stan Celestian. Queensland Agate, Poppy Jasper (yellow with red inclusions): Courtesy of Captain Tenneal.