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Quartz is the mineral with the greatest amount of varieties. The chemical formula of quartz is quite simple SiO2, but the range of colors, form of occurrences, and the presence of optical effects are multiple. Quartz is accompanying humans for several thousand years and during this period it gathered numerous amount of names, which usually change from country to country. We will guide you through all the varieties of quartz known today.
Quartz varieties are rock crystal, milk quartz, amethyst, citrine, ametrine, smoky quartz, morion, tiger’s eye, hawk’s eye, and aventurine. Microcrystalline quartz varieties are jasper, carnelian, chalcedony, onyx, agate, chert, and flint. Structural varieties are tridymite, cristobalite, coesite, and stishovite.
Sometimes quartz forms such unusual forms that can be mistaken even with diamonds. Quartz can occur as beautiful crystals and cryptocrystalline aggregates, where no crystals can be observed, but colorful layers form intriguing patterns.
Quartz is even found in meteorite craters and some varieties can be formed after a meteorite fall. The Quartz family even has its own ‘diamond’, which name is the Herkimer diamond. This variety of quartz forms two ended crystals and resembles the diamond’s outline.
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Different Varieties of Quartz
Quartz occurs in nearly all types of rocks and geological environments. You can find it in acid igneous, metamorphic, and sedimentary rocks. It is highly resistant to weathering (7 on the Mohs scale) and tends to concentrate on sandstones and other detrital rocks. And even can from masses of rocks (sandstone) composed of quartz grains only.
Quartz varieties can be divided into two main groups and let’s say some phenomena.
The first group of quartz crystals is composed of well-known rock crystals, amethyst, citrine, ametrine, milky quartz, smoky quartz, and morion.
The second group is microcrystalline varieties of quartz known as jasper, carnelian, chalcedony, onyx, agate, chert, and flint.
Optical varieties of quartz are the next. They are aventurine quartz, and various ‘eyes’ (tiger’s eye, hawk’s eye, cat’s eye). Also, we will mention included quartz varieties here.
The most widespread is utilized quartz, where a gold-colored needle-like crystal of rutile (titanium oxide) is included in transparent quartz. Other minerals can be found in quartz crystals: elbaite, actinolite, and chlorite. And the separate occasion is oil inclusions.
Depending on the habitus of quartz crystal, scepter quartz and Herkimer’s style quartz (double-terminated quartz crystals) can be distinguished.
And here we need to mention structural varieties of quartz (polymorphs), which form under high-pressure, high-temperature conditions (from 20-80 kbar, from 800 up to 1750 oC).
Why Does Quartz Have So Many Varieties?
The main reason is the different formation environments. Because of the different temperatures and pressure during the quartz formation, different impurities can get into the quartz structure.
Different colors of quartz varieties are explained by impurities of various elements (Ti, Fe, Mg, Mn, Al) and inclusions of other minerals.
Microcrystalline varieties of quartz are subdivided based on the grain size, by the character of bands or opacity. No doubt, that formation environment is a clue of diversity in this group, too. These quartz varieties are mostly found in sedimentary rocks.
Optical varieties are divided based on the optical effect, whether it is the cat’s eye effect triggered by inclusions of other minerals of elongated (needle-like form), or the aventurine effect (inclusions of isometric minerals).
High-temperature/high-pressure varieties of quartz are the result of elevated pressure and temperature and are usually found in meteorite craters because only the fall of an extraterrestrial body can generate such tremendous heat and pressure.
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- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
How Many Different Kinds of Quartz Are There
In this article, we are going to mention 29 varieties of quartz. The list of varieties provided is more than enough even for sophisticated collectors or geoscientists.
Here are some of the most common varieties you can find at every mineral fair or show based on the color:
| Name of Quartz Variety | The Color of Quartz Variety |
|---|---|
| Rock crystal | Clear, colorless |
| Milky quartz | Translucent white |
| Rose quartz | Milky pink, translucent. Color is due to titanium, iron, and manganese impurities. |
| Amethyst | Purple. Color is due to “holes” of missing electrons in the crystal structure in combination with iron impurities. |
| Citrine | Yellow, light orange. Color is due to iron impurities. |
| Praseolite | Green, yellow-green. Color is due to iron impurities and mineral inclusions (chlorite). |
| Smoky quartz | Transparent brown or gray. Its color is due to “holes” of missing electrons in combination with aluminum impurities. |
| Morion | Black smoky quartz, almost opaque. |
TIP: Do you know how to test the hardness of quartz or any other rock or mineral? The best option is to use Mohs Scale Test Kits. Check out the best Mohs Scale Test Kits in the article below:
3 Best Mohs Scale Test Kits: Test Hardness of Your Gemstones
What Are the Varieties of Quartz?
So do you know how many varieties of quartz are there? Well, you might be surprised so let’s start!
Rock crystal
Rock crystal is a colorless and transparent quartz type of quartz. It is found mainly in the cavities of hydrothermal veins. It is also found in miarolitic voids of pegmatite veins and contact-metamorphic deposits of various types.
It is very common in sedimentary rocks, but does not form large crystals there, but is found in the form of crystal brushes on the walls of cracks and the form of geodes, mainly among limestones and in calcareous strata.
Amethyst
Amethyst is the most popular purple variety of quartz. It is usually found in the form of druses, brushes, and geodes. The color of amethyst can be very intense and depends on the admixture of iron in the mineral. The stone can lose color under the influence of high temperatures at 200 ° C.
Amethyst is highly sought after by the geodes it forms. The geodes can reach up to several meters high. The source of this miracle made by nature is Brazil and Uruguay.
Amethyst is a truly magnificent stone, which can be found not only in the special geological environment but also in each nature-lover collection.
Citrine
The next quartz variety is named due to its lemon color. Citrus – lemon yellow, hence the name is “citrine”.
The color of the stone varies. It is a pale yellow, juicy lemon, bright honey. The color depends on impurities, ferric iron, tetravalent silicon, and trivalent aluminum.
Even being a variety of the most widespread stone, natural citrine is very rare. Most stones available now on the market are mostly heated amethyst.
Ametrine
A rare two-tone stone that combines the names and colors of two quartz varieties described above at the same time – amethyst and citrine.
Ametrine or bolivianite is a by-color variety of quartz. In ametrine crystals, the color is distributed unevenly over the zones of growth, with alternating areas of purple-lilac amethyst and yellow citrine. It is mined at the Anai mine (Anahai), dep. Santa Cruz, Bolivia (an original location that gives the name Bolivianite).
Today it’s extremely hard to find a natural ametrine. The material represented on the market is mostly synthetic quartz or heated amethyst.
Strawberry Quartz
Strawberry quartz or cherry quartz is originally known as “scarlet quartz” and was used in the late nineteenth century to describe fine-grained red hematite including quartz from the iron mines of Cumbria, England.
The name strawberry quartz has also been used in the early 21st century when referring to various synthetic substances under the pretense that the material is natural quartz.
Smoky Quartz
Smoky quartz or rauchtopaz is a smoky variety of crystalline quartz from gray to dark gray and brownish-gray (but not black) color. It is transparent or moderately flawed by fluid inclusions.
Smoky quartz occurs in the form of crystals, sometimes very large (up to 1 m and more), often forming beautiful aggregates and druses. The occurrence of giant crystals of smoky quartz weighing up to several tons has been reported.
Smoky quartz deposits are widespread throughout the world. They are mainly of hydrothermal origin and are confined to cavities within large quartz veins.
TIP: Did you know you can find smoky quartz near volcanoes? Yes, it is true. And not just smoky quartz but many other beautiful rocks and minerals. Find out more in the article below:
Ten Most Common Types of Rocks You Can Find In Volcanoes
Morion
Morion (or mormorion) is black crystal quartz, and in contrast to smoky quartz, it is opaque. The color is a result of a structural defect (an electron-hole formed when the Si4+ ion is replaced by the Al3+).
It is found in high-temperature hydrothermal veins, in miarolitic cavities of granite pegmatites, and in greisens. Individual single crystals from pegmatites reach hundreds of kilograms or more.
Milk Quartz
Milk quartz or milky quartz is the most common variety of crystalline quartz. The white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation.
Rose Quartz
Rose quartz is a type of quartz that exhibits a pale pink to rose red hue. The color is usually considered due to trace amounts of titanium, iron, or manganese in the material.
Rose quartz doesn’t form well-faceted crystals and druses. It is usually found as a translucent rose-color mass.
TIP: Quartz is the most common mineral on earth, and the minerals in the feldspar group make up almost 60% of the earth’s crust. Find out the differences between quartz and feldspar in the article below:
Feldspar vs. Quartz: What’s the Difference? 5 Crucial Signs
Praseolite
Praseolite is a translucent variety of quartz, which has a green color due to thin inclusions of actinolite, chlorite, or other green minerals.
Aventurine
Aventurine is quite a valuable and popular inexpensive decorative and ornamental stone because of its beautiful shimmering due to numerous inclusions of small flakes of mica or hematite
Aventurine is opaque, and fragile, with a glassy luster. The color of aventurine is usually yellowish to honey-yellow or brownish-red, cherry-red, pinkish to almost white, and rarely green or bluish.
Nowadays, the material called “aventurine” is usually an imitation of real aventurine made of glass obtained by adding tiny flakes of copper to the glass mass.
The Tiger’s Eye
The tiger’s eye is a parallel fibrous aggregate of quartz with ingrowths of a certain amount of fibers of alkaline amphibole.
The Hawk’s Eye
The hawk’s eye is approximately the same as the tiger’s eye, but the amphibole mineral is not oxidized.
Chert and Flint
Chert and flint, very fine-grained quartz.
Several varieties are included under the general term chert: jasper, chalcedony, agate, and flint.
Flint is gray to black and nearly opaque (translucent brown in thin splinters) because of included carbonaceous matter.
Opaque, dull, whitish to pale-brown or gray specimens are simply called chert; the light color and opacity are caused by abundant, extremely minute inclusions of water or air. Chert and flint provided the main source of tools and weapons for Stone Age men.
TIP: Despite being among the most common and abundant minerals on earth, quartz is highly sought after! Find out more about finding quartz on the beach in the article below:
Can You Find Quartz on the Beach? It Depends How You Look
Chalcedony
Chalcedony is a cryptocrystalline fine-fiber type of quartz.
It has many varieties itself, painted in different colors:
- Carnelian – reddish
- Chrysoprase – greenish
- Sapphirine – bluish.
Banded chalcedony, consisting of layers that differ in shade, transparency, and density, is called agate.
Stones with parallel straight stripes and layers are called onyx.
Chalcedony is a fairly common mineral, mainly among sedimentary rocks. It is also common in igneous rocks, where at the postmagmatic stage it fills partially or completely gas voids and cracks with the formation of geodes and agates. Occasionally found in low-temperature hydrothermal veins.
Herkimer Diamond Quartz
Found in Herkimer County, New York the Herkimer diamond is a form of natural quartz crystal with two pointed ends. These crystals have the typical hexagonal form of quartz; however, instead of having a termination on one end, they are doubly terminated. This is a result of the crystals growing with very little or no contact with their host rock.
This type of quartz does not adhere to dolostone (dolomite and limestone), so the quartz trapped inside these air pockets trapped in dolostone did not adhere to the surrounding matrix stone.
This left the quartz crystals free to crystallize unattached to the matrix stone and allowed both of their ends to grow into terminated points.
This type of quartz is documented in locations from all over the world, but in most cases, it has different local names. Because of its untypical form, the Herkimer diamond quartz is very popular among mineral collectors.
TIP: Quartz is a hard and crystalline mineral that consists of two oxygen and one silicone atom. It takes years to form this mineral under intense pressure. Find out more in the article below:
Forming of Quartz Crystals & Its Varieties Explained by PRO
Tridymite and Cristobalite
At temperatures above 867 °C (1,593 °F), quartz changes its structure from tridymite and cristobalite.
Coesite and Stishovite
At very high pressures (more than 20 kbar) quartz transforms into coesite and, at still higher pressures, stishovite. Such phases have been observed in impact craters.
These quartz varieties are extremely rare as can be found in meteorite craters only and usually became a subject of scientific research and eventually goes to a museum or private collections.
FAQ about Quartz Varieties
Still, have more questions about quartz? Below you will find frequently asked questions that have not yet been answered:
Does rauchtopaz is topaz?
It is misleading or sometimes a trading name for smoky quartz. Rauchtopaz name was used in the past due to its approximate visual similarity to topaz, but the chemical composition and crystal structure of topaz and quartz differ significantly. It’s better to avoid misleading names and never hesitate to ask questions to mineral sellers.
Does chalcedony is also quartz? It looks different.
Chalcedony and all its own varieties of the chemical formula are SiO2, the same as quartz. The only difference is that quartz in its classical perception forms beautiful crystals while chalcedony does not.
Chalcedony is a cryptocrystalline variety of quartz. It forms from a colloidal watery solution of silica which is not visible under a microscope.
Is Herkimer diamond quartz? Maybe, it was in the past?
Herkimer diamond is a misleading name also. It’s more correct to call such quartz a Herkimer’s style quartz to avoid any misunderstanding. The only feature that is similar to diamond is a form of quartz crystal. The composition, structure, and formation process are absolutely different.
If quartz is so widespread, can it be safe to buy quartz anywhere?
The fact that quartz is so widespread and cheap mineral cannot protect you from buying a fake or dyed material. Please, pay attention, especially to the next varieties of quartz: citrine, ametrine, agate, aventurine, cat’s eye, and strawberry quartz.
Conclusion
Quartz has a lot of varieties. They can be differentiated by color, crystal form, and the geological environment they crystallize. We tried to provide you with an essential list of quartz varieties, drawing your attention to the most common one and highlighting some rare species and features.
TIP: So now you know what the varieties of quartz are. But do you know how the different varieties of quartz are valuable? Find out more in the article below:
How Much is Quartz Worth? Value for Common Quartz Varieties