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Quartz identification and geology

A very common rock-forming mineral composed of silicon dioxide SiO₂ in a three-dimensional framework of SiO₄ tetrahedra. Quartz is characterized by its Mohs hardness of 7, lack of cleavage, conchoidal fracture, vitreous luster, and hexagonal crystal habit when well-formed. It occurs in virtually every geological environment and has numerous varieties including amethyst, citrine, rose quartz, smoky quartz, chalcedony, agate, and jasper. Field: mineralogy. Example: Quartz is the second most abundant mineral in the Earth's continental crust after feldspar, and clear quartz crystals from the Alps 'rock crystal' have been valued since antiquity.. Related terms: Silica, Framework silicate, Chalcedony, Conchoidal fracture.

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  • Conchoidal fracture

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.055955+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Quartz mean in geology?
A very common rock-forming mineral composed of silicon dioxide SiO₂ in a three-dimensional framework of SiO₄ tetrahedra. Quartz is characterized by its Mohs hardness of 7, lack of cleavage, conchoidal fracture, vitreous luster, and hexagonal crystal habit when well-formed. It occurs in virtually every geological environment and has numerous varieties including amethyst, citrine, rose quartz, smoky quartz, chalcedony, agate, and jasper.
What is an example of Quartz?
Quartz is the second most abundant mineral in the Earth's continental crust after feldspar, and clear quartz crystals from the Alps 'rock crystal' have been valued since antiquity.
Which earth-science field uses the term Quartz?
Quartz is used in mineralogy.
Which terms are related to Quartz?
Related terms in this reference are Silica, Framework silicate, Chalcedony, Conchoidal fracture.

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