Quartz Stone – Characteristics, Colours and Varieties

Quartz is the ideal gemstone for jewellery and is one of the few coloured stones you’ll find in almost every jewellery shop.

Quartz is one of the main constituents of granite and other igneous rocks. It is also commonly found in sedimentary rocks and is a common component of metamorphic rock.

Well-formed crystals can reach incredibly large sizes, often exceeding several metres in length and weighing over a hundred kilos.

Quarter stone - chalcedony variety
Quarter stone – chalcedony variety

The best quality crystals are destined for the optics, electronics and instrumentation industries (considered the biggest consumers), while those of lower quality are destined for industry in general (abrasives, ceramics, metallurgy).

Quartz is the second most abundant mineral on Earth and is found in 12 per cent of the planet, in places such as Brazil, Madagascar, the United States and others.

Because of its abundance, quartz crystal has many uses in society. As well as being used in jewellery, it appears in cosmetics, watches, computers, radios and even in construction.

Quartz is a silicon oxide (SiO2) and is found in nature in polymorphous forms: quartz, tridymite and cristobalite.

As the temperature changes, phase transformations occur, each of which is given a specific name.

Pedra de Quartzo - Caracteristicas, Cores e Variedades

Quartz has properties that remain constant over time and, on the Mohs Scale, it has a hardness of 7 out of the 10 levels available.

This means that it is very resistant to falls and scratches.

In general, its lustre is vitreous, which gives the stone a very beautiful luminosity. So when it comes to making a piece of jewellery, the end result is a delicate and certainly charming piece;

In terms of crystal quartz production, the states of Bahia, Minas Gerais, Goiás, Paraná, Rio de Janeiro, São Paulo and Santa Catarina stand out.

This stone is usually white or colourless. However, it can have different colours depending on the impurities present in its formation.

Quartz Crystal
Quartz Crystal

Quartz is the ideal gemstone for jewellery

It is easily available and quite affordable.

Even large stones can be bought at excellent prices. Quartz is also one of the few coloured stones that you’ll find in almost every jewellery shop.

Amethyst and citrine are official birthstones and are often used in birthstone jewellery.

As most quartz is untreated, there are many astrological uses for different types of quartz gemstones (carnelian, for example), so you can find many planetary jewellery designs with quartz.

Quartz is also often used to make fine watches, including bezels and moving parts.

Quartz is durable enough to wear in quartz gemstone rings every day and is also ideal for any other jewellery application available.

Quartz gemstones can be worn by men or women, as they can be found in almost any colour imaginable.

You can find quartz in any style of cut and shape, from cabochons to faceted stones, as well as dropped and pierced beads.

Quartz is also often carved into interesting ornamental designs, such as paperweights, animal sculptures or as seals, carvings and insignia;

There are two main varieties of quartz, which can be subdivided into other more specific varietal names. 

Main Gems and Precious Stones
Main Gems and Precious Stones

Two main branches of quartz include

1. macrocrystalline

Macrocrystalline quartz includes amethyst, rock crystal, blue quartz, citrine, hawk’s eye, prasiolite, cat’s eye quartz, smoky quartz, rose quartz and tiger’s eye.

Macrocrystalline quartz is typically transparent to translucent and forms with larger crystals than cryptocrystalline quartz.

2. Cryptocrystalline

Cryptocrystalline quartz forms with microscopically small crystals, which in most cases cannot be seen even under magnification. Cryptocrystalline quartz mixed with moganite, a polymorph of quartz, is referred to as chalcedony.

Chalcedony actually includes a wide variety of quartz gemstones, including agate, chrysoprase, bloodstone, jasper and carnelian. Chalcedony ‘in the strict sense’ usually refers only to lighter, single-coloured chalcedony, usually bluish in colour.

Cryptocrystalline quartz is generally opaque or translucent in clarity;

Quartz stone

1. Colours and types of crystals

The colour of macrocrystalline quartz is as variable as the spectrum, but clear quartz is by far the most common colour, followed by white or cloudy quartz.

Purple (amethyst), pink (rose quartz), grey or brown to black (smoky quartz) are also common.

Cryptocrystalline quartz varieties can be multicoloured. Under artificial light, quartz does not have a desirable quality. It looks best in daylight, especially after sunrise and just before sunset. The deep colours are the most valuable;

There are different types of quartz crystals available in nature. Below, we’ve selected the main ones:

  • Colourless quartz: the most common, also called rock crystal;
  • Amethyst: this is lilac or purple coloured quartz, the colour of which is due to the presence of iron or manganese ions in its composition;
  • Pink quartz: this is the second most common type, with different shades of pink resulting from the presence of titanium impurities in the stone;
  • Smoky quartz: has levels of aluminium in its composition, which results in colours ranging from yellow to dark brown, almost black;
  • Citrine: has a light yellow, orange or reddish colour and its hue can be natural or the result of a heat treatment carried out on the amethyst;
  • Milky quartz: has a white colour and is more opaque, which gives it its milky appearance, which is actually the result of tiny inclusions;
  • Agate: this is a cryptocrystalline variety of quartz, i.e. made up of minerals so fine that they cannot be identified even at microscopic level.

Amethyst is a purple variety of the mineral Quartz, and its most valuable and prized variety. Its purple colour is usually caused by impurities of iron or manganese compounds;

2. Clarity and Brilliance

Fine quartz is transparent, which means that light passes through the stone unhindered.

In translucent quartz, the passage of light through the stone is slightly weakened. The best quality quartz is “clean”, free of inclusions of any kind.

As quartz is abundant, there is little reason to choose stones with visible inclusions, except those that define the character of the stone (e.g. cat’s eye, hawk’s eye or scenic stones).

The lustre is vitreous to vitreous like crystals, while cryptocrystalline forms are generally waxy to opaque, but can be vitreous.

Crystals are transparent to translucent; cryptocrystalline forms are generally translucent or opaque;

3. Cut and Shape

Due to the roughness of the colour distribution in crystals, quartz is often cut into bright circles to maximise its colour.

Other cuts can be used when the colour is better distributed.

Quartz is available in a wide range of sizes and calibrated shapes, including many sophisticated forms;

4. Treatment

Colourless quartz is always untreated.

Coloured stones can occasionally be enhanced by dyes (as in the case of agate), irradiation (bombardment with a low level of radioactivity) or heating.

Some stones can also be impregnated or coated with wax, transparent resin and even foil to enhance colour, shine and stability.

Synthetic quartz is also abundant. Naturally coloured quartz usually exhibits colour zoning;

5. How to look after your jewellery

  • Jewellery with quartz crystals doesn’t require complicated care. Cleaning, for example, should only be done with running water, using a soft cloth to dry it.
  • Other than that, avoid leaving your pieces exposed to direct sunlight and watch out for drops or knocks.
  • By taking each of these issues into account, you’ll have beautiful, long-lasting quartz jewellery.

Synthetic quartz

Synthetic quartz is often found in colours that do not occur naturally. In many cases, the colour is simply too vivid and intense to be a natural occurrence;

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