Difference Between Quartz and Calcite (With Table)

Minerals refer to the elements or chemical compounds which are formed due to various geological processes. These minerals are predominantly crystalline. All the minerals have different chemical compositions and properties. They also have different physical properties. They are used for different purposes. Quartz and Calcite are two such minerals.

Quartz vs Calcite

The difference between Quartz and Calcite is that quartz is much stronger than calcite. The two minerals look very similar. There are also a couple more differences between the two minerals. The major differences can be found in terms of their hardness, shape, luster, cleavage, and appearance.

Quartz is a mineral composed of silica or silicon dioxide. The term has its origin in the German word ‘Quartz. It is a really hard mineral that is commonly found in a hexagonal shape. It is available in different forms. This crystal also comes in a wide variety of colors.

Calcite is a mineral that is a carbonate mineral with a rhombic cleavage. The term has its origin in the German word ‘Calcit’. It is a moderately hard mineral that is also available in different forms. This crystal’s appearance is white or opaque. The color can change if it is charged with impurities.

Comparison Table Between Quartz and Calcite

Parameters of ComparisonQuartz Calcite 
HardnessIn comparison, quartz is approximately four times harder. In comparison, calcite is approximately four times less hard. 
ShapeThey are commonly found in the shape of a hexagonal prism.They are commonly found in the shape of a rhombohedron.
LusterTheir appearance is mostly glassy or it can also have a vitreous luster.It can have a luster that is vitreous or resinous or dull.
CleavageIt is not equipped with strong cleavage.It has a rhombic cleavage.
Chemical CompositionIn terms of chemical composition, it is a silicon dioxide crystal.In terms of chemical composition, it is a calcium carbonate mineral. 

What is Quartz?

This term has originated from the German word ‘Quarz.’ It is a part of the trigonal crystal system. It is extracted from open cast mines. Quartz refers to a mineral that is hard and crystalline. This mineral is composed of silica or silicon dioxide. The overall chemical formula given is SiO2. The second most copious mineral found is Quartz. Its existence comes in two different forms, they are as follows-

  • The Normal quartz or the Alpha (α)- quartz
  • The High- temperature quartz or the Beta (β)- quartz

Both the quartz are chiral. The Normal quartz or Alpha (α)- quartz can be transformed to High- temperature or Beta (β)- quartz at 573 °C. This transformation comes along with a major change in volume. This change can lead to ceramic, or rock fracture passed through the temperature threshold.

The quartz comes in many varieties. Most of them are also semi-precious stones. They are one of the most commonly used stones for jewelry making and carvings. Clear quartz, Amethyst, Citrine, Rose quartz, Smoky quartz are some of the popular quartz available. It is also believed that these are healing stones. They are used by several people for obtaining calmness, love, peace, and other things.

What is Calcite?

Calcite refers to a carbonate mineral. This mineral is also the most stable polymorph of calcium carbonate. Aragonite and vaterite are the other polymorphs of calcium carbonate. Aragonite has the ability to transform into calcite. This can take place over days or even quicker with temperatures above 300 °C. The term calcite has originated from the German word ‘Calcit.’ It is also related etymologically to chalk.

This mineral comes in various forms. There are more than 800 identified forms of Calcite. Out of these formsScalenohedra and rhombohedral are the most common ones. In terms of hardness, it has a defining value of 3 on the Mohs Scale of Mineral Hardness. In terms of appearance, it is opaque or has a white color. However, if the mineral is charged with certain impurities, it can change its color. The changed color is not defined; it may change into any shade, including black.

An optical property termed birefringence is displayed by a calcite crystal. This property is also known as double refraction. Due to which the objects that are seen through the crystal seem to have doubled. As it is a carbonate mineral, it can dissolve in acids. This crystal too is used for many purposes, including jewelry making and carvings. This mineral too is believed to have healing properties. 

Main Differences Between Quartz and Calcite

  1. In comparison, quartz is approximately four times harder. In comparison, calcite is approximately four times less hard.
  2. Quartz is commonly found in the shape of a hexagonal prism. Calcite is commonly found in the shape of a rhombohedron.
  3. The appearance of quartz is mostly glassy, or it can also have a vitreous luster. Calcite can have a luster that is vitreous or resinous, or dull.
  4. Quartz is not equipped with strong cleavage. Calcite has a rhombic cleavage.
  5. Quartz, in terms of chemical composition, is a silicon dioxide crystal. Calcite, in terms of chemical composition, is a calcium carbonate mineral.

Conclusion

Quartz and Calcite are two of the most commonly found minerals. One is silicon dioxide whereas, the other is a carbonate mineral. In comparison, the quartz is harder than the calcite. Both the minerals are found in many different forms. The appearance of both the minerals is also quite different.

Quartz is available in different colors like blue, yellow, purple, and so on. Whereas the calcite is always white or opaque. However, if it is charged with any impurities, the color of the calcite mineral can change. The color can be of any shade. These minerals are widely used around the globe for different purposes.

References

  1. https://www.osapublishing.org/abstract.cfm?uri=josa-49-7-710
  2. https://www.ajsonline.org/content/263/9/747.short
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