Travertine Onyx Sculptures Travertine onyx is a travertine which is extremely hard, at least the onyx spots. Travertine is a form of limestone with lots of holes and valleys made by water eroding the rock. It can be quite colored, depending on which chemicals were in the water. See piece T2. A chart of these colors and chemical names is given below. The color of a mineral comes from the principal chemical it contains. The minerals in the water during the formation process provides the coloration of the stone. For example : - yellow (sodium chromate) - orange (potassium dichromate) - red (cobalt nitrate) - mauve (cobalt chloride hexahydrate) - blue (copper sulfate pentahydrate, ferric hexacyanoferrate) - purple (potassium permanganate) - green (nickel chloride hexahydrate)

Published: March 01, 2017