Skip to main content Skip to Search Box
Summary Article: Arkose
from Rock and Gem

A RELATIVELY COARSE SANDSTONE, arkose consists primarily of quartz and feldspar grains with small amounts of mica. It has a high feldspar content (more than 25 per cent of the sand grains), setting it apart from other sandstones. Its grains tend to be moderately well sorted, angular or slightly rounded, and usually cemented with calcite, although they can sometimes be cemented with iron oxides or silica. Arkoses are presumed to derive from granites and, like them, are pink or gray. Sandstones with a feldspar content of 5–25 per cent are called subarkoses.

  • Properties
  • Rock type Terrestrial, marine, or freshwater detrital, sedimentary
  • Fossils Rare
  • Major minerals Quartz, feldspar
  • Minor minerals Mica
  • Color Pinkish to pale gray
  • Texture Medium, angular

Sediments

These Torridonian sediments containing arkose were deposited in north-west Scotland.

Thin section

This medium-grained feldspathic red sand-stone is from Pre-cambrian sediments at Stoer, Scotland.

© 2008 Dorling Kindersley Limited

Related Articles


Full text Article sandstone
The Columbia Encyclopedia

sedimentary rock formed by the cementing together of grains of sand. The usual cementing material in sandstone is calcium carbonate, iron oxides, or

Full text Article sandstone
The Dictionary of Physical Geography

An indurated sedimentary rock composed of cemented particles of sand, with a range of grain sizes between 0.0625 and 2 mm. They can be subdivided in

Full text Article Arkose
Guide to Minerals, Rocks and Fossils

Colour Red, pink or grey. Texture Medium-grained, but usually nearer to the coarse end of the scale; grains angular. Structure Bedding may...

See more from Credo