biology daily - the biology and biochemistry encyclopedia
biology daily articles and research Encyclopedia Dictionary Forums biology research links Weblinks Pictures Articles Blogs Newsletter

Onyx

This article is about the mineral. See Onyx (disambiguation) for other meanings

Onyx is a banded variety of chalcedony, a cryptocrystalline form of quartz. The colours of its bands are white and black. It is usually cut as a cabochon, or into beads, and is also used for intaglios and cameos. Some onyx is natural but much is produced by the staining of agate.

Technical details
Chemical composition and name SiO2 - Silicon dioxide
Hardness (Mohs scale) 7
Specific gravity 2.65 - 2.66
Refractive index (R.I.) 1.543 - 1.552 to 1.545 - 1.554
Birefringence 0.009
Optic sign Positive
Optical character Uniaxial

See also



07-14-2008 23:18:10
The contents of this article are licensed from Wikipedia.org under the GNU Free Documentation License. How to see transparent copy
BiologyDaily.com 2005. Legal info   Privacy