Roger Weller, geology instructor
Quartz Family Gemstones-by Audrey LaClair
Sardonyx is a form of Chalcedony. It’s colors are usually bands of reddish-brown and white, but can be many varieties. The bands are made up of small quartz fibers in layers, which give the banded appearance. There are some instances where sardonyx is natural, but most of the time it is from stained agate.
Sardonyx is usually used for beads, but can also be used for cameos and intaglios. It is also used for gemstones, where it is found to be relatively inexpensive. Sardonyx can be found in India, Uruguay, Czechoslovakia, Brazil, and Germany. In the USA, it is usually found in Oregon and around Lake Superior. Sardonyx originated in Pakistan.
Sardonyx can also be known as the “gem of courage”. It gets it’s name from the Greek language from sard which means “reddish brown” and onyx which means “veined gem”.
Sardonyx is thought to let the wearer have irresistible charisma. It is also known for cleansing the kidneys and liver and for warming. It is said to help the wearer have more discipline and to be able to see the past or future, as well as many other qualities.
Chemical Composition and Name: SiO2 - Silicon Dioxide
Specific Gravity: 2.65-2.66
Refractive Index (R.I.): 1.543-1.552 to 1.545-1.554
Optic Sign: Positive
Optical Character: Uniaxial