opalescence 20
Precious opal ("black matrix opal") in Tertiary-aged vesicular basalt from Honduras. A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical...
Precious opal ("black matrix opal") in Tertiary-aged vesicular basalt from Honduras. A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are about 5400 named and described minerals – about 200 of...
