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Forming of Quartz Crystals & Its Varietes Explained by PRO

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Quartz is a hard, crystalline mineral composed of two oxygen and one silicone atom. It takes years to form this mineral under extreme pressure. Quartz is the second most abundant mineral in the Earth’s crust and is thought to be the crystalline form of silicon dioxide. However, the process of forming quartz crystals is extremely complex, requiring immense pressure over many years.

Quartz is a mineral found almost everywhere. It occurs under a wide range of mineral-forming conditions and can be found almost anywhere on Earth. It can be igneous, metamorphic, or sedimentary in origin. Quartz has the greatest number of varieties. They differ in color, structure, and mode of occurrence.

Today, you will learn about the different geological environments of quartz crystals and how they are formed in those locations. Moreover, you will also learn the chemical formulae that go behind creating these crystals. You will also learn the conditions necessary to form quartz crystals at high pressures.

How are quartz crystals formed
How are Quartz Crystals Formed?

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How Quartz Crystals Are Formed?

Magmatic quartz forms as a result of silica-rich magma solidification. Quartz crystallizes during the last stages of igneous rock formation. Also, quartz forms by precipitation from silica-rich hydrothermal solutions in veins and vugs. Quartz can form during extreme metamorphic conditions.

The term “quartz” comes from a German word, “Quarz,” which means “hard.” On the other hand, the Ancient Greeks called quartz “krustallos.”

This term was derived from the Ancient Greek word “kruos,” which means “icy cold.” Together, these words became Quartz Crystal in the English language. The chemical formula for quartz crystal is SiO2.

Quartz Crystals are formed via hydrothermal processes and can be found in three different geological formations. These environments are:

  • Silica-rich molten rock when it is cooling down and solidifying
  • Pegmatites during the pneumatolytic processes
  • Watery solutions of silica under high temperatures and pressures

These quartz crystals generally use hydrothermal processes to add molecules to their surface and grow layer by layer. Let’s examine how quartz crystals are formed in all three different environments.

How Do Quartz Crystals Form in Igneous Rocks?

Macrocrystalline Quartz is among the most essential elements for forming igneous rocks, such as silica-rich molten or pegmatite rocks.

These quartzes are either present before the rocks are formed or are developed along with other minerals when the rocks are being formed. These quartzes later turn into quartz crystals via the hydrothermal process due to:

  • An Abundance of Silica
  • High Temperatures
  • Intense Pressures

Igneous rocks, such as molten rocks, are a mixture of positively charged metal cations:

  • Potassium, K+
  • Calcium Ca2+
  • Water

Moreover, these rocks also contain negatively charged anions, such as:

  • Phosphate ion [PO4]3-
  • Silicate ion [SiO4]4-

However, there are no SiO2 molecules in igneous rocks that serve as the founding elements for quartz crystals.

If you have ever seen lava before it is turned into molten rock, you must have wondered about the reason behind its viscosity.

This viscosity directly results from flexible molecules that tend to swim through the lava. Another reason behind this viscosity is the high amount of silica present in the rock itself. This silica makes the lava more viscous and plays a vital role in forming quartz crystals.

These flexible molecules are negatively charged. Moreover, these also contain hydrogen atoms in hydroxyl groups (-OH) in abundance. However, the relation of [O-] to [OH] relies heavily on the amount of water in the lava itself.

Since the molten magma cools quickly, typically during the volcanic eruption, the period becomes too limited for the bonds in the SiO4 chains to split apart and form ordered structures of crystallized silicates.

When this lava cools down, it turns into volcanic glass. Therefore, it can be understood that a high viscosity level plays a negative role in forming crystals and serves as an obstacle in this formation.

On the other hand, a low viscosity level allows the bonds to quickly split and form new bonds of structured, ordered crystals, enhancing the overall process of crystal formation.

This also shows that silica-rich lavas have a higher chance of forming quartz crystals.

If the lava bursts and comes outside the Earth’s crust, it will cool down quickly. On the other hand, if the magma stays inside the Earth’s crust, it will cool down slowly, allowing quartz crystals to form.

The magma inside the crust will start to cool down eventually and form minerals and crystals of different chemical compositions depending upon the nature of the magma and its attributes.

Quartz crystals are the last to be formed inside molten or igneous rocks. Therefore, these crystals fill out the voids and pockets of air that were left untouched during the formation of other minerals, such as:

  • Mica Crystals
  • Feldspars
  • Cryptocrystalline Quartz

This order of formation also determines some of the most important elements of quartz crystal, such as:

  • Shape
  • Weight
  • Overall dimensions

Additionally, quartz crystals formed inside igneous rocks also offer an onion shape, meaning these crystals come with layers and layers of molecules hardened into crystals.

These outer layers take time to form, and you can see a significant difference in the color of different interior and exterior layers of a quartz crystal found inside a rock.

TIP: Both quartz and feldspar are classified as silicates since their chemical composition includes silicon. In addition, both mineral types are often found in the same rock. Check out the main differences between these two minerals in the article below:
Feldspar vs. Quartz: What’s the Difference? 5 Crucial Signs

Is Quartz Metamorphic or Igneous?

A complex description of quartz crystallization in igneous rocks can make you think this is the only way to quartz formation. However, quartz can also be formed as a result of high pressure and temperature during metamorphic processes.

Quartz can be found in all three types of rocks (igneous, metamorphic, and sedimentary). Quartz can be formed in different ways. It can be crystallized directly from magma (to be of igneous origin) and can be formed during metamorphism due to previous minerals’ recrystallization.

How Do Quartz Crystals Form in Watery Solutions?

Hot watery solutions, known as hydrothermal environments, are a hotbed for quartz crystals in their purest forms. The hydrothermal process takes place at temperatures between 100°C and 450°C and requires high pressures to form the quartz crystals fully.

[SinOm]-OH + H4SiO4 → [Sin+1Om+2]-OH + 2 H2O

If you ever want to create orthosilicic acid, you can reverse this reaction and turn quartz crystals into this acid:

SiO2 + 2 H2O → H4SiO4 

First, the individual orthosilicic acid molecules are dissolved into a hot water solution to increase the amount of silica in this solution.

These molecules quickly increase the amount of silica and create a hospitable and appropriate environment for the formation of quartz crystals.

These molecules either come from the nearby rocks, or from a scientist for an experiment. These hot water solutions are also quite rich in terms of ions and carbon dioxide. If the temperature or pressure drops, silica solubility decreases so that the quartz solution is saturated.

Once the H4SiO4 compounds are applied to quartz grains in neighboring minerals, the crystals form a solution. If quartz grains are empty in the adjacent rocks, the H4SiO4 molecules add to form small floating crystals that bind H4SiO4 molecules more and more.

Only in a sufficiently oversaturated solution is this random forming of crystals feasible. The  SiO4 tetrahedra are fully integrated into the quartz crystal.

On the other hand, if the temperature and pressure changes are constant and slow, there will no longer be small crystals.

However, the existing crystals will continue to grow, and SiO4 tetrahedra will be added one layer at a time to enhance further and complete these existing crystals.

Steady temperature ensures crystal formation, whereas, rapid changes in temperature essentially form smaller crystals and do not allow a full-fledged formation of crystals.

The formation of new crystals is not a pre-defined feature but depends on the temperature changes. Slow growth and constant temperature changes result in the formation of larger crystals. Fast growth and rapid changes result in the formation of odd-shaped smaller crystals.

The reason is that growth isn’t just because molecules are added to crystals constantly, it is the net result of molecular addition as well as removal.

Therefore, constant changes in temperature and pressure play a vital role in the overall formation of quartz crystals.

Moreover, during the formation of crystals, the molecules tend to chip away from the edges due to weaker bonding. This is why smaller crystals often get dissolved again during the hydrothermal process.

When the temperatures fall, the following things decrease as well:

  • The solubility of silica
  • The mobility of the H4SiO4
  • The supply of new molecules
  • The growth of the crystals will stop

Moreover, if there are hot brines in the equation, these will cause the entirety of the rock to cool very quickly. This external element will result in the formation of the white vein or gangue quartz.

On the other hand, depending on the size of the lava body and the presence of hot watery solution in the cracks, the cooling process may take up to thousands of years.

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Is Quartz a Solid or a Liquid?

After reading the previous passage, you can assume that quartz can occur in a liquid state also, but this is not true.

Quartz occurs in a solid state only. The definition of a mineral is a solid, natural, inorganic substance with a regularly repeated inner structure. When magma is liquid, it is a mixture of many elements (not only Si and O). When these two elements crystallize into solid material, they can be called quartz.

How Long Does It Take For Quartz to Form

Quartz formation requires gradual and slow cooling of magma or gradual precipitation from hydrothermal solution. It takes thousands of years for quartz crystals to form. Quick processes produce microcrystalline or massive semi-transparent quartz without any right form of crystals. 

Where Does Quartz Naturally Occur

Quartz is a ubiquitous mineral. It is the second most abundant mineral in the Earth’s crust. Because of quartz’s omnipresence, it is probably the first mineral known and used by humans.

Quartz naturally occurs in all types of rocks: igneous, metamorphic, and sedimentary. It can be found in granites, gneisses, and sandstones. Crystals can be found in vugs; massive milky quartz occurs in veins. The whole rock can be made of quartz grains exceptionally, and it’s called quartzite.

Beautiful crystals of quartz can be found in vugs or fissures. Geologists from different parts of the world have reported that several meters of quartz crystals from pegmatite veins are present. Commonly, quartz can be observed in sand and pebbles on every seaside or riverside. It can be found in your backyard or near a railroad.

TIP: Minerals’ streak is one of the most important tests for mineral identification, especially while working with native metals and sulfide minerals. Find out more in the article below:
DIY Guide: Testing Mineral’s Streak (Explained by Expert)

What Are the Physical Properties of Quartz Crystals?

Quartz crystals are highly resistant to powerful chemical and mechanical weathering and are highly durable in nature.

This is why these crystals are most commonly found on mountaintops, beaches, and desert sand. Let’s take a look at some of the properties of Quartz.

Chemical FormulaSiO2
CompositionSilicon dioxide
ColorColorless, white, purple, pink, brown, and black, gray, green, orange, yellow, blue, and red, multi-colored or banded
Crystal SystemTrigonal
TransparencyTransparent to opaque
Specific Gravity2.6 – 2.7
LusterVitreous. Transparent, colorless Quartz crystals from a few distinct localities may be adamantine.
CleavageIndiscernible. Seldom exhibits parting.
Other ID MarksSome specimens fluoresce, especially white and green.Triboluminescent.Piezoelectric.
Complex TestsDissolves in hydrofluoric acid
In GroupSilicates; Tectosilicates; Silica Group
Striking FeaturesHardness, crystal forms, striations on crystal faces, and the frequent appearance of conchoidal fractures on crystal faces.
EnvironmentQuartz occurs in almost every single mineral environment.
Rock TypeIgneous, Sedimentary, Metamorphic
Popularity (1-4)1
Prevalence (1-3)1
Demand (1-3)1
Physical Properties of Quartz Crystals

TIP: Do you know you can find quartz on the beach? Yes, and it is quite simple to do so! Check out this article, and you can get started:
Can You Find Quartz on the Beach? It Depends on How You Look

What Are the Different Uses of Quartz?

Quartz is widely used in optical devices, telephone and radio equipment (as a piezoelectric), as well as electronic devices (for stabilizing the frequency of electric generators). It is heavily consumed by the glass and ceramic industries (rock crystal and pure quartz sand). Many varieties are used in jewelry.

Quartz crystals are among the most abundant minerals found in the crust of our planet, and therefore, these crystals are used in a variety of things. Their physical and chemical properties make them suitable for a wide array of uses.

Quartz Crystals have a hardness level of 7 Mohs, and this makes them perfect for a modern era production process. Let’s take a look at some of the uses of quartz crystals.

How Are Quartz Crystals Used in Glass Making?

In most modern geological processes, the extracted sand is almost made entirely of 100% quartz grains. These sand deposits are also known as one of the highest-purity silica sand deposits.

Therefore, these sand deposits are used primarily for glassmaking. Quartz sand is used in the production of:

  • Container glass
  • Flat plate glass
  • Specialty glass
  • Fiberglass

Firstly, these sand deposits are melted into a liquid at high temperatures and pressures of 1700°C (3090°F). Once the sand deposit is melted, it doesn’t revert back to its original state upon cooling down. However, it does transform into an entirely different semi-liquid state with a new structure.

This semi-liquid state never turns into a completely solid state, no matter how much it cools down. This frozen liquid state is also known as an amorphous solid, and it is also considered a cross between a solid and liquid with a crystalline structure that is later converted into the form of glass. This amorphous solid is then mixed with:

  • Waste glass collected from recycling
  • Soda ash (sodium carbonate)
  • Limestone (calcium carbonate)

This combination of amorphous solids and other elements is then heated in a furnace up to a temperature of 1700 F.

The soda ash helps reduce the overall melting point of this sand deposit, and it also helps the manufacturer save energy costs and utility costs during the process.

If you only include soda ash in this mixture, it will produce glass that can easily be dissolved in any liquid or water. To prevent this drawback, limestone (calcium carbonate) is added, which offers enough robustness to the glass so that it doesn’t dissolve in any liquid.

This is how silica-high sand deposits are converted into glass with the help of high temperatures and other elements.

How Is a Quartz Crystal Used as an Abrasive?

As already discussed, sand deposits with a high quantity of silica come with a powerful rating of seven on the Mohs scale.

Quartz crystals are quite harder than other naturally occurring substances and are also found most abundantly in Earth’s crust. This is what makes them excellent abrasive materials Quartz sands can be used for:

  • Sandblasting
  • Scouring cleansers
  • Grinding media
  • Grit for sanding
  • Sawing

How Is Quartz Used as A Foundry Sand?

Since Quartz is naturally extremely resistant to chemicals and heat, it becomes an excellent material to be used as foundry sand.

Quartz offers a high melting temperature that is considered to be higher than the majority of metals. Therefore, Quartz can easily be used for the molds and cores of common foundry work.

Quartz is most often used for refractory bricks that offer a high level of heat resistance and durability to homeowners and factory owners.

What Are Some Other Uses of Quartz Crystals?

Another amazing quality of quartz crystals is their ability to vibrate at specific frequencies without any trouble.

This is why you must have seen the word Quartz written on many analog timepieces.

Quartz crystals can vibrate at specific frequencies in such an accurate manner that these can be used to make accurate time-keeping instruments and equipment without the need for any other electrical or mechanical component.

These quartz crystals are also used to transmit the majority of radio and television signals with amazing accuracy at stable frequencies, and that is why these are used for satellites and signal processing.

Back in the 1920s, crystal oscillators were created with the help of naturally found quartz crystals. These oscillators helped the soldiers keep accurate time and maintain constant radio communication with other soldiers on the battleground.

Nowadays, quartz crystals are used for:

  • Analog watches
  • Satellite radio transmitters
  • Equipment that requires vibrational accuracy for performance

These quartz crystals are also used by the majority of modern manufacturers for the purpose of GPS meters and devices that can help pinpoint the right direction without any need for electrical components.

Quartz crystals are also used in lasers and help enhance the overall intensity of laser beams without breaking apart. This is because quartz crystals can tolerate a higher level of heat and chemical reactions without giving up.

TIP: No gemstone’s value is as elusive and variable as quartz. Do you know how valuable quartz crystals can be? Find out the answer in the article below:
How Much is Quartz Worth? Value for Common Quartz Varieties

How Many Different Varieties Exist for Quartz Crystals?

Different varieties of Quartz Crystals

How Many Different Varieties Exist for Quartz Crystals?

  • Amethyst

This is a purple-colored variety of Quartz. These are quite similar to the natural crystalline form of Quartz and offer almost the same attributes to the users.

  • Aqua Aura

This form of Quartz is synthetically enhanced with the help of a coating. This coating is a father created from gold and other metals. The coating also gives these crystals a neon blue or other neon color.

  • Aventurine

An opaque form of compact Quartz contains small mica, hematite, or goethite scales. These scales offer a glistening effect.

Aventurine is also classified as a rock because of its natural chemical composition, which is quite similar to several minerals. However, the majority of scientists see this form as a variety of Quartz.

  • Blue Quartz

As a blue variety of Quartz, faith healers most commonly use it to offer healing qualities to the users. It is highly uncommon in nature and rarely in crystal form.

  • Cactus Quartz

This form of Quartz is a large crystal or a combination of different and multi-colored crystals overgrown with a layer of spiky smaller crystals.

That means that smaller and sharper crystals are grown on top of the cactus quartz. Cactus quartz can only be found in Boekenhouthoek (Magaliesberg), South Africa.

  • Chalcedony

One of the most common forms of Quartz is a specific, microcrystalline form of Quartz. It is quite similar to naturally occurring Quartz in terms of chemical composition; however, it has a different structure, where Quartz crystals are so tiny that they cannot be seen with the naked eye.

  • Citrine

This form of Quartz is often found in yellow, orange, or brown colors. These can often be a combination of these colors.

  • Faden Quartz

These are different groups of quartz crystals. These groups come with a white thread-like zone that runs through the interior vessels and veins of crystals.

The remaining layers of crystals are basically formed around the thread axis of the white-threaded zones and veins.

  • Ferruginous Quartz

This form of Quartz comes with an opaque red-to-brown Hematite coating. These give off a neon-ish color scheme and often have internal inclusion.

  • Herkimer Diamond

Noted as one of the most beautiful and lustrous forms of clear quartz crystals, it is a completely transparent form of quartz crystals. It comes specifically from the Herkimer Co. vicinity in the Mohawk Valley region of Central New York State.

  • Milky Quartz

If you are looking for a white and translucent form of Quartz. It is also considered among the most beautiful and natural forms of quartz, giving it a transparent look of milky white.

  • Morion

This is yet another opaque and translucent form of Quartz that primarily comes in black. It is also called smoky quartz due to its black color scheme.

  • Phantom Quartz

It was named Phantom Quartz because it is known to grow internal phantom growths. These ghostlike layers are formed over hundreds of years within a crystal due to the remains of hot water solutions trapped inside cavities of the pre-formed crystal.

  • Prase

These beautiful quartzes come in different colors ranging from light to emerald green. Moreover, these are also transparent or translucent, depending upon the natural composition of the surrounding rocks. The colors are also based on the elements found in the surrounding regions.

  • Praseme

If you want to take a look at some of the most beautiful and gorgeous light green and translucent forms of Quartz with Hedenbergite inclusions, Praseme is the one for you.

These are quite beautiful, and the color comes from the minerals found in the host rock. These quartz crystals are primarily found on Serifos Island, Greece.

  • Prasiolite

These kinds of quartz crystals are artificially colored and come in a light green color scheme. These crystals are colored with the help of modern heat treatment of certain types of Amethyst crystals that can be found naturally in igneous rocks. These are also referred to as Green Amethyst Crystals.

  • Rainbow Quartz

This form of quartz crystals is also known to be synthetically colored to appear rainbow-ish in nature.

It is synthetically colored with the help of heat treatment and made to look like an iridescent layer formed from gold or other metals. These are quite similar to aqua aura quartz crystals in terms of composition and color schemes.

  • Rock Crystal

A colorless and transparent form of quartz crystals, it is most commonly found in the form of a large crystal and can be found in volcanic caves and igneous rocks that are thousands of years old.

  • Rose Quartz

Healthcare practitioners also use this form of pink quartz crystals for a wide array of healthcare benefits and skin treatments. You must have heard the term rose quartz roller from beauty experts.

  • Rutilated Quartz

If you are looking for the form of quartz crystals with golden yellow, needle-like rutile inclusions, the rutilated quartz crystals are the answer.

  • Scepter Quartz

This form of quartz crystal comes with a scepter-like protrusion on the end of the crystal. This scepter-like protrusion is wider than the rest of the crystal. The second generation of silica-bearing fluids explains the unusual form.

  • Smoky Quartz

These types of quartz crystals can be found in different color schemes ranging from brown to black. These darker color schemes often give these crystals a touch of smokiness.

  • Star Quartz

This is a variety of quartz crystals exhibiting asterism in the form of a six-rayed star. These are also naturally polished on the exterior and contain a six-rayed star quality.

  • Tourmalinated Quartz

These quartz crystals come with splintery tourmaline inclusions.

TIP: If you want to know more about quartz varieties, check out the complete guide in the article below:
Complete List of Quartz Varieties: Know Them All!

What Is the Bottom Line Here?

Quartz Crystals are formed through a process known as the hydrothermal process, which involves hot water solutions, silica-rich minerals or rocks, and high pressures and temperatures. These quartz crystals result from the layer-by-layer addition of SiO2 molecules on the surface.

In general, when igneous rocks cool down, they form pockets filled with hot, watery solutions. When these cool down, this results in a slow formation of crystals with the help of SiO2 molecules.

These quartz crystals are among the most commonly found minerals in the crust and are widely used in the production of glass, foundry sand, and other useful items.

Moreover, these crystals are also used for the purpose of oscillation and time-keeping, as these can vibrate at precise frequencies without getting disturbed.

TIP: Many people use the terms rock, mineral, crystal, stone, and gemstone interchangeably, but these terms have specific meanings in the world of rockhounds. Find out more here:
Rock, Mineral, or Crystal? What’s the Difference?