Golden beryl

Gem quality beryls are aquamarine (blue), emerald (green), and golden beryl. Likewise, amethyst b a violet-colored silica, and sapphire (blue) and ruby (red) are alumina. Yet pure beryl (Be,AI>Si lO ). alica (SiO ). and alumina (AI O>) are colorless. Explain... 

CHRYSOBERYL. The mineral chrysoberyl. an aluminaie of hery Ilium corresponds to the formula BeALO. , crystallizes in the orthorhombic system with both contact and penetration twins common, often repeated resulting in ro.setted structures. Hardness. 8.5 specific gravity. 3.75 luster vitreous color various shades of green sometimes yellow. A variety which is red by transmitted light is known as alexandrite. Streak colorless transparent to translucent, occasionally opalescent. Chrysoberyl also is known as cymopbane and golden beryl. 

An example of a cyclosiHcate is beryl BejAljSi Ojg (Figure M58). It usually occurs in green, bluish-green, yellow or pink hexagonal prisms. Transparent and colored gem varieties include emerald, aquamarine, heliodor and golden beryl. In the tourmaline... 

Heliodor is the golden yellow gem variety of beryl due to the isomorphous substitution of aluminum by ferric cations. It is also known as yellow beryl if the golden tint lacking. Good colored material is relatively rare. As other gem varieties of beryl it is found in granitic pegmatites in Brazil in the Ural Mountains (Russia), and Namibia. 

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