Silicates · Sourced PROFILE

Quartz

SiO₂

One of Earth's most abundant minerals, occurring in many geological environments.

AT A GLANCE

Formula: SiO₂
Crystal system: Trigonal
Space group: P3₁21 or P3₂21 (low quartz)
Mohs hardness: 7
Density: 2.65 g/cm³
Optical character: Uniaxial (+)

CRYSTALLOGRAPHY

Crystal form & structure

Commonly a six-sided prism terminated by rhombohedra; also drusy, fibrous, microcrystalline as chalcedony, or massive. More than 500 crystal forms are reported.

HAND-SAMPLE PROPERTIES

Physical properties

Cleavage: Rarely observable; poor on rhombohedral and prismatic directions
Fracture: Conchoidal
Tenacity: Brittle; tough when massive
Streak: White
Luster: Vitreous; waxy to dull in massive varieties
Transparency: Transparent to nearly opaque
Observed colours: Colourless, white, grey, purple, yellow, pink, brown, black, and many inclusion-derived colours

LIGHT & OPTICS

Optical properties

Optical class: Uniaxial (+)
Refractive index: ω 1.544; ε 1.553
Fluorescence & electrical behaviour: Usually inert; response varies with inclusions. Piezoelectric and pyroelectric, and sometimes triboluminescent.

GEOLOGICAL SETTING

Formation

Forms in igneous, metamorphic, sedimentary, and hydrothermal settings.

MINERAL COMPANY

Common associations

Feldspars, micas, calcite, fluorite, tourmaline, and a very wide range of ore and rock-forming minerals

FIELD NOTES

How to identify it

Hardness 7 scratches ordinary glass; conchoidal fracture and absent obvious cleavage separate it from feldspar. Calcite is much softer and reacts with dilute acid.

NAME & HISTORY

Where the name comes from

The name has medieval German roots; its earlier origin is uncertain.

SCIENTIFIC SOURCE

Handbook of Mineralogy — Quartz

External reference; factual profile paraphrased and attributed. Copyright remains with the publisher.

Open reference PDF

PROVENANCE

Documented occurrences

South Tien Shan

Dara-i-Pioz alkaline massif · Quartz-rich boulders host rare-mineral assemblages documented by modern mineral descriptions. The record is regional and does not disclose a collection point.

Sourced · ApproximateLocality precisionKalyuzhnyite-(Ce), a new mineral from the Dara-i-Pioz alkaline massif