Quartzolite or silexite is an intrusive

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

, in which the

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

is more than 90% of the rock's

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

mineral content, with

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

at up to 10%. Typically, quartz forms more than 60% of the rock, the rest being mostly feldspar although minor amounts of

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

may also be present. Quartzolite occurs as dykes, sills,

vein Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and feta ...

s, bosses and segregation masses; it is also found in association with greisen and

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic c ...

. Quartzolite is an extremely rare type of rock. No extrusive rock equivalent of quartzolite is known.

Synonyms

The use of the synonym "''silexite"'' is discouraged because it is the French word for

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

, which is a

sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...

. Other less common synonyms are "''igneous quartz''" and "''peracidite''".

Examples

* Chrastava, Czech Republic * Crag Mountain, Northfield, Massachusetts, United States * Jabal Hamra, Saudi Arabia * Keivy,

Kola Peninsula The Kola Peninsula (; ) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely inside the Arctic Circle and is border ...

, Russia * Lyon Mountain quadrangle, New York state, United States * Moulting Pond, Newfoundland, Canada * Qiabukanzhuota, China * Saveh County, Iran * Smaaland Cove,

South Georgia South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

* South Mountains, Arizona, United States * Torrington, New South Wales, Australia

Formation

Some occurrences of quartzolite are unlikely to have an entirely igneous origin; for example, two types of quartzolite that are associated with deposits of topaz in and around the Mole

Granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

pluton in Torrington, NSW, are believed to have formed in different ways. One type forms dykes and sills in the granite and in the surrounding metamorphic rocks. The other type has remnants of an earlier granite texture and is found on the outer edges of part of the pluton.

References

{{Rock type Intrusive rocks