Name/Title
Onyx Stone EggEntry/Object ID
2004.5.21Description
Chemical Composition: Slo2 Silicon Dioxide
Description: Salmon orange color with black rings 3 inches long
Onyx is a cryptocrystalline form of quartz. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx available contain bands of colors of white, tan, and brown. Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Pure black onyx is common, and perhaps the most famous variety, but not as common as onyx with banded colors.
It has a long history of use for hardstone carving and jewellery, where it is usually cut as a cabochon, or into beads, and is also used for intaglio or cameo engraved gems, where the bands make the image contrast with the ground. Some onyx is natural but much is produced by the staining of agate.
The name has sometimes been used, incorrectly, to label other banded lapidary materials, such as banded calcite found in Mexico, Pakistan, and other places, and often carved, polished and sold. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as 'onyx' today are this carbonate materiTechnical details Chemical composition and name SiO2 - Silicon dioxide
Hardness (Mohs scale) 7
Specific gravity 2.65 - 2.667
Refractive index (R.I.) 1.543 - 1.552 to 1.545 - 1.554
Birefringence 0.009
Optic sign Positive
Optical character Uniaxial
al.[1]
Rock Origin: Post-depositional
Rock Type: Igneous
Specific Gravity: 2.65-2.67Collection
Suomynona Mineral CollectionAcquisition
Accession
2004.5Source or Donor
Suomynona Egg CollectionAcquisition Method
DonationLocation
Category
PermanentMoved By
Scott LonganDate
October 29, 2009Location
Shelf
BottomCabinet
Case # 7Room
Mentzer HallBuilding
Crater Rock MuseumCategory
Permanent