Catherine Bell (I) Catherine was born in London, but moved to California with her Iranian mother at age 2. Her mother still acts as her personal assistant. As a child, she acted in various TV adverts. She went to UCLA to study biology, but dropped out to become a model in Japan.
When gemstones are identified by category, the following categories may apply: 1  Diamonds â considered the most precious stone in the world. 2  Corundum â contains gemstones like sapphires and rubies. 3  Chrysoberyl â alexandrite and catâs eyes are two common stones of this type.here are other ways to evaluate types of gemstones. People may classify them by hardness on the Mohs scale, by color, by rarity, or by popularity. What is really most important in considering different types is how they appeal and how well they will hold up when used in certain ways.
Even some of the black gemstones above â hematite, jet and obsidian in particular â are not categorically precious or semi-precious stones; but these black stones are used as ornaments. Other black rocks made into jewelry include amphibolites, lodestone, tektite and lava.ike white moonstones, the black gemstones hail from the group of minerals called feldspars, along with sunstone, oligoclase and andesine. The black semi-precious stones are not necessarily black entirely, but may be grey, interspersed in many cases with the beige and white of the more well-known moonstone.