The gems of the orthopyroxene series are usually very dark slightly brittle because of cleavage and generally not. The traditional list of gemstones that are considered precious stones are. The semi precious s gems value importantly depends on color their substances and their quality because these stones have more sources they have a wide range of substances and occur in a variety of colors. The brown and green gems from tanzania are enstatites as are the brownish green stones from sri lanka. These terms are based on old traditions from the west.
All other gemstones are considered as being semi precious stones. These days all gemstones are considered precious since they are all rare and there is a limited supply of them. All other stones are considered semi precious stones. All other quality stones are called semiprecious even though they may not be any less valuable or beautiful. A gemstone which is semi precious does not mean it is less valuable than precious gemstones.
The only precious gemstones are diamond ruby sapphire and emerald. The only precious gemstones are diamond ruby sapphire and emerald. All other gemstones are considered as being semi precious stones. The gems of the orthopyroxene series are usually very dark slightly brittle because of cleavage and generally not.
