Mineraloid "Opal"


Virgin Valley, Humboldt County, Nevada, USA, private collection from Netherlands.

Opal is a hydrated amorphous form of silica. Mineralogically, opal is a hydrous silicon dioxide. It is amorphous, without crystalline structure, and without a definite chemical composition (it contains a variable amount of water). Therefore opal is a mineraloid rather than mineral. Lovely Butterscotch and milk colored common opal. The condition of the sample is good. Age-related wear, fractures and minor cracks may appear. Dirt and dust may exist. Size approx.  4,0cm x 3,9cm x 2,8cm. Weight c. 46g.