- Education and Science
Facts About Quartz—Properties, Types, & Uses
Quartz is a mineral found in many rocks. It is one of the most common minerals found on earth.
Quartz was known since pre-historic times and appreciated for its beauty. "Krsitallos" was the ancient name recorded for quartz by Theophrastus in about 300-325 BCE.
This mineral is a crystalline form of silica. It can be found as a major component of igneous, metamorphic and sedimentary rocks. It belongs to a group of minerals called silicates. Quartz can also be found in the form of small grains as sand in the mountains, beaches, rivers and deserts.
Quartz crystals dissolve in water at high temperatures and pressure. When this water seeps into rocks through cracks and fissures, it forms thin white seams and large veins of quartz that may extend to distances of over many kilometers.
Structure and Forms of Quartz
Structure of Quartz
Quartz is made of continuous chains of silicon and oxygen atoms arranged in the framework of tetrahedra.
Each silicon atom is surrounded by and connected to four oxygen atoms, and each oxygen atom is connected to two silicon atoms.
Crystal Structure of Quartz
Quartz crystals are hexagonal in shape and belong to the trigonal crystal system. The ideal trigonal crystal system is a six-sided prism that terminates with six-sided pyramids at each end. They frequently occur in twin form where two crystals are joined at the base at 90 degrees.
The quartz crystals occur in nature as huge prismatic crystals, stubby crystals or a pointed collection of prismatic and stubby crystals.
Forms of Quartz
Quartz occurs in two primary forms in nature the macrocrystalline and the microcrystalline also known as the cryptocrystalline form.
Macrocrystal quartz is made of crystals that are visible. The rose quartz and the smoky quartz are examples of the macrocrystal quartz form.
Microcrystalline Quartz is made of tightly packed tiny crystals and crystallites that are visible only under a microscope. Agate, Jasper, Onyx are examples of the microcrystalline quartz form.
The piezoelectric effect was discovered in 1880 by two French physicists, brothers Pierre and Paul-Jacques Curie in quartz crystals of Tourmaline and Rochelle salt.
Properties of Quartz
Pure quartz is colorless and transparent; it is also known as rock crystal or clear quartz. It can withstand chemical and mechanical weathering and does not break down easily.
Quartz is one of the hardest minerals on earth measuring 7 on the Mohs Scale of Hardness.
Pure quartz is transparent and colorless, but impure quartz occurs in many colors such as white, gray, purple, yellow, brown, black, pink, green and red.
Quartz is a piezoelectric material. The word piezoelectric refers to the ability of the quartz crystal to convert mechanical stress into electricity and vice versa.
When a mechanical stress is applied to a quartz crystal, the crystal converts the mechanical stress into electricity, and when electricity is passed through a quartz crystal, it converts the electricity into a mechanical force that results in the crystal vibrating at a particular frequency.
Modern day watches use the quartz crystal to keep accurate time. The quartz crystals have the ability to maintain an accurate frequency standard that helps to regulate the movement of quartz watches.
Piezoelectricity is used in ultrasound equipment, microphones, record players, in spark lighters and inkjet printers.
What is the Mohs scale of hardness?
Mohs hardness is a scale that is used to measure the resistance of a smooth surface to scratching or abrasion by a substance of known or defined hardness. This scale was devised by a German Mineralogist, Friedrich Mohs.
The Mohs scale ranges from 1 – 10 in which 1 represents a material very easily scratched and 10 represents the hardest material highly resistant to scratching or abrasion.
Quartz measures 7 on the Mohs scale of hardness and diamond, the hardest material, measures 10.
Types of Quartz Based on Color
Pure quartz is also called rock crystal. Pure rock crystal has a very small percentage of impurities. It is colorless, transparent or translucent.
Colored quartz crystals are valued for their color and beauty and are used as gemstones. Quartz colors are the result of traces of other minerals present in quartz crystals.
The following is a list of the different types of quartz by color.
Transparent to Translucent
Transparent to Nearly Opaque
Blue, Green, Yellow, Orange, Brown, Gray
White, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Multicolored
Black base with White Upper Layer
Red, Brown, Yellow
Translucent to Opaque
Light Grayish Brown to Deep Black
Transparent to Translucent
Yellow, Brown, Multicolored
Yellow, Yellow-Brown, Orange, Dark Orange-Brown, Reddish-Brown
Transparent to Translucent
Pale Gray Green to Deep Grass Green
Uses of Quartz
Deposits of sand that have almost 100 % pure silica have been found in some locations. The sand from these deposits is used in glassmaking industry to produce container glass, flat plate glass, specialty glass, and fiberglass.
Quartz is a hard mineral and measures seven on the Moh’s scale and is an excellent abrasive substance. Quartz sand is used for sand blasting, as scouring cleansers for grinding and grit for sanding and sawing.
Flux for Smelting Metals
Quartz is mechanically and chemically strong, durable and has a melting temperature that is higher than most metals. These properties make quartz an ideal mineral to make refractory bricks and as a flux in the smelting of metals.
Pure quartz is also known as the frac sand that is used in the petroleum industries for the process of hydraulic fracturing (fracking) that facilitates the flow of petroleum fluids such as oil, natural gas liquids and natural gas from the rocks into the bore well.
Quartz sand with maximum purity is forced down oil and gas wells under high pressure. The high pressure fractures the rocks, and the sand slurry flows into the fracture. The quartz sand that is hard and durable keeps the fractures open without getting crushed and facilitates the flow of oil and natural gas into the bore well.
The piezoelectric nature of quartz crystals has been utilized in manufacturing industries to make watches and equipment such as radios, televisions, electronic games, computers, cell phones, electronic meters and GPS equipment.
Nowadays quartz crystals are grown in laboratories based on the product for which it is being used. They can be grown in different shapes, sizes, and colors specifically needed for the manufacturing process.
As a Gemstone
Quartz is hard and durable and occurs in nature in a variety of colors. The colorful quartz crystals are used as gemstones to make jewelry.
Quartz is a mineral found in many rocks. It is one of the most common minerals found on earth. Quartz is made of continuous chains of silicon and oxygen atoms arranged in the framework of tetrahedra.
Quartz is one among the hardest minerals on earth measuring 7 on the Mohs Scale of Hardness. This quality of quartz has made it an integral part of manufacturing industries. Colored quartz crystals are used as gemstones and some of the crystals are said to have healing properties.