Aquamarine is one variety of the mineral beryl. It is found ranging in color from light blue to dark blue and also blue-green. It is most commonly known as the birthstone for March. The word aquamarine is Latin for sea water. Aquamarine has a hexagonal crystal system and is usually transparent, but can be opaque. It has a hardness of 7.5-8 and a refractive index of 1.564-1.596. It is a brittle stone and is sensitive to pressure. The most desired color is dark blue. However, lower quality gems can be heated to 725-800 degrees F to change them to the darker color. This change is permanent. Unfortunately, higher heat will cause discoloration in the stone. Inclusions are rarely found in aquamarine and usually cause the gem to be more fragile. Occasionally a gem cam be found with a cat's eye effect. It is often found in pegmatites and coarse-grained granite. Aquamarine is mined in many places including Brazil, Russia, Australia, Tanzania, Kenya, Nigeria, and many other countries. The largest finding of gemstone quality was in Brazil in 1910. It was 18 inches long and 15 1/2 inches in diameter and weighed in at 243 pounds. It produced many stones with a total weight of more than 100,000 carats.