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As the mineral with the most known varieties, quartz displays an incredible diversity despite its simple chemical formula of SiO2. For thousands of years, quartz has accrued many different names across cultures, usually referring to distinct colors, optical effects, crystal shapes, and geological occurrences documented worldwide.
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 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; some varieties can be formed after a meteorite falls. The Quartz family even has its own ‘diamond,’ Herkimer. This variety of quartz forms two-ended crystals and resembles the diamond’s outline.
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Different Varieties of Quartz
Quartz is found in nearly all types of rocks and geologic settings. They are found in acidic igneous rocks such as granite and metamorphic and sedimentary rock. Additionally, they are highly resistant to weathering (rating 7 on the Mohs hardness scale). It concentrates on sandstones and other detrital rocks, sometimes even forming pure quartz sandstone.
There are two main groups of quartz varieties, as well as some special phenomena:
- Well-known crystalline varieties include rock crystal, amethyst, citrine, ametrine, milky quartz, smoky quartz, and morion quartz.
- Microcrystalline varieties include jasper, carnelian, chalcedony, onyx, agate, chert, and flint.
- Optical varieties show special effects. Examples are aventurine quartz with shiny inclusions, tiger’s eye, hawk’s eye, and cat’s eye quartz. Some quartz contains long rutile crystals or mineral inclusions like tourmaline, actinolite, chlorite, or petroleum fluids.
Quartz also shows growth patterns like scepter quartz or Herkimer-style double-terminated quartz crystals.
With time, it can transform into other mineral structures like tridymite, cristobalite, coesite, and stishovite under high pressure and temperature conditions during metamorphism.
Scepter quartz and Herkimer-style double-terminated quartz crystals can be distinguished based on the crystal habit.
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. Due to differences in temperature and pressure during quartz formation, different impurities can enter the quartz structure.
The different colors of quartz varieties are explained by impurities from various elements (Ti, Fe, Mg, Mn, Al) and inclusions of other minerals.
Microcrystalline varieties of quartz are subdivided based on grain size and the character of bands or opacity. Undoubtedly, the formation environment contributes to the diversity in this group as well. These quartz varieties are mostly found in sedimentary rocks.
Optical varieties are divided based on the optical effect, whether the cat’s eye effect is triggered by inclusions of elongated (needle-like) minerals or the aventurine effect from isometric mineral inclusions.
High-temperature/high-pressure quartz varieties result from elevated pressure and temperature. They are usually found in meteorite craters, as only the fall of an extraterrestrial body can generate such tremendous heat and pressure.
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How Many Different Kinds of Quartz Are There
This article mentions 29 varieties of quartz—more than enough even for sophisticated collectors or geoscientists.
Here are some of the most common quartz varieties, sorted by color, that you’ll find at any mineral fair or gem show:
| 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 the Mohs Scale Test Kits. Check out the best Mohs Scale Test Kits in the article below:
3 Best Mohs Scale Test Kits: Test the Hardness of Your Gemstones
What Are the Varieties of Quartz?
Did you know there are over 29 varieties of quartz? Let’s explore some of the most popular ones.
Rock Crystal
This colorless, transparent form of quartz is also called clear quartz. It’s most often found in the cavities of hydrothermal veins and miarolitic voids within pegmatite veins. Rock crystals also occur in contact-metamorphic deposits and sedimentary rocks, forming crystal brushes, coating crack walls and filling geodes, primarily in limestones.
Amethyst
The most popular purple variety, amethyst, forms druses, brushes, and gorgeous geodes. Its deep color comes from iron impurities. Too much heat (over 200°C) can cause amethyst to fade.
Some of the largest amethyst geodes—up to several meters tall—are in Brazil and Uruguay. These natural marvels make amethyst a prized collector’s item.
From hydrothermal veins to personal collections, amethyst is a magnificent quartz variety in many geological environments.
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 though it is a variety of the most widespread stones, natural citrine is 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 simultaneously – amethyst and citrine.
Ametrine or bolivianite is a by-color variety of quartz. In ametrine crystals, the color is distributed unevenly over the growth zones, with alternating purple-lilac amethyst and yellow citrine areas. 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 was originally known as “Scarlet quartz.” It was used in the late nineteenth century to describe fine-grained red hematite, including quartz from the iron mines of Cumbria, England.
In the early 21st century, “strawberry quartz” referred to various synthetic substances. These are falsely marketed as natural quartz.
Smoky Quartz
Smoky quartz or Rauchtopaz is a smoky variety of crystalline quartz with colors ranging from gray to dark gray and brownish-gray (but not black). It is transparent or moderately flawed by fluid inclusions, tiny bubbles, or cavities trapped inside the quartz.
Smoky quartz occurs in the form of crystals, sometimes very large (up to 1 m and more), often forming beautiful aggregates and druses (crystalline crusts coating rock surfaces).
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 hydrothermal origin and confined to cavities within large quartz veins.
TIP: Did you know you can find smoky quartz near volcanoes? Yes, it’s 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 a black crystal quartz that is opaque in color compared to smoky quartz. The color results from a structural defect (an electron-hole formed when the Al3+ replaces the Si4+ ion).
It is found in high-temperature hydrothermal veins, in miarolitic cavities of granite pegmatites, and 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 exhibits a pale pink to rose red hue, which comes from trace titanium, iron, or manganese impurities in the mineral. Rose quartz doesn’t form well-faceted crystals and druses (crystalline crusts coating surfaces). 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 green quartz. Its color comes from inclusions of minerals like actinolite and chlorite.
Aventurine
Aventurine is a popular decorative aggregate containing inclusions that create a glistening optical effect. Its most common colors are:
- Yellowish to honey-yellow
- Brownish-red
- Cherry-red
- Pinkish to almost white
- Rarely green or bluish
Aventurine has an opaque and fragile appearance with a glassy luster. Nowadays, the material marketed as “aventurine” is often an imitation made of glass with added copper flakes.
The Tiger’s Eye
Tiger’s eye quartz contains parallel fibers of quartz along with fibrous mineral deposits.
The Hawk’s Eye
The hawk’s eye is approximately the same as the tiger’s, 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 earth’s most common and abundant minerals, 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 on 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, Herkimer diamond is a variety of natural double-terminated clear quartz crystals.
Unlike typical quartz formations, these crystals have terminations at both ends. This unique form occurs because the crystals grow unattached inside air pockets in the dolostone host rock.
The crystals do not adhere to the surrounding dolomitic limestone. This allows them to develop defined points on both ends as they crystallize freely within the rock pockets.
While similar formations occur globally, the “Herkimer diamond” is tied to New York’s Herkimer County locale. Their unusual shape makes these quartz crystals particularly popular among mineral collectors.
TIP: Quartz is a hard and crystalline mineral that consists of two oxygen and one silicon 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 they can be found in meteorite craters only and usually become a subject of scientific research and eventually go to a museum or private collection.
FAQ about Quartz Varieties
Still have more questions about quartz? Below, you will find frequently asked questions that have not yet been answered:
Is Rauchtopaz Topaz?
The term “Rauchtopaz” can be misleading, as it is sometimes used as a trade name for smoky quartz. The name stems from a past attempt to liken its visual appearance to topaz, but Rauchtopaz and true topaz have very different chemical compositions and crystal structures. Quartz and topaz are separate mineral species.
It is advisable to avoid inaccurate marketing names like “Rauchtopaz” and always feel empowered to ask mineral sellers clarifying questions. Open communication builds trust in transactions and enables one to make informed purchasing decisions rather than relying upon vague visual resemblances or incorrect aliases. Understanding the true geological origins of minerals is important.
Does chalcedony is also quartz? It looks different.
Chalcedony and all its varieties of 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 different.
If quartz is so widespread, can it be safe to buy quartz anywhere?
The fact that quartz is so widespread and is a 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 occurs in over 29 varieties that can be distinguished by color, crystal shape, and geological formation. This article covered some of the most prominent types of quartz—from the common varieties found in many mineral collections to rarer finds tied to specific locales.
We focused on key identification features for the major quartz varieties, highlighting traits like color origins and crystal habits. Special attention was given to ubiquitous types like clear rock crystal purple amethyst, and unusual oddities like double-terminated Herkimer diamonds.
TIP: So now you know what the varieties of quartz are. But do you know how valuable the different varieties of quartz are? Find out more in the article below:
How Much is Quartz Worth? Value for Common Quartz Varieties