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Beryl is composed of beryllium aluminum silicate and is the chief ore of the element beryllium. Crystals of beryl in certain unique rocks called pegmatites can be as large as railroad boxcars. These immense crystals are never transparent, but some pegmatites contain smaller, well formed and transparent beryl crystals; these occur in various colors, and each variety used as a gemstone has its own special name. The green variety is called simply green beryl. This is very different from the unique dark green variety known as emerald. Large fine beryl crystals occur in Brazil, Russia, Madagascar and many other places. The hexagonal (6-sided) symmetry of the mineral is evident in this crystal from Mursink, Russia.