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.
- 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
Colour Red, pink or grey. Texture Medium-grained, but usually nearer to the coarse end of the scale; grains angular. Structure Bedding may...
A feldspar-rich, coarse-grained sandstone derived from the erosion of granite and composed of angular to subangular, poorly to moderately...
Sandstone that is rich in feldspar, with 10-25% feldspar and less than 20% matrix material; intermediate in composition between pure quartz...