Gemstone usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons. Gemstones are classified into different "groups", "species", and "varieties". For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow) and morganite (pink), which are all varieties of the mineral species beryl. Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture and luster. They may exhibit pleochroism or double refraction. They may have luminescence
USS Aquamarine (PYc-7) USS Aquamarine (PYc-7) USS "Aquamarine" (PYc-7) was a patrol boat in the United States Navy during World War II. Later known as Miss Ann, the ship was listed on the U.S. National Register of Historic Places in 1998. "Aquamarine" was built in 1925 by Pusey and Jones Corporation, Wilmington, Delaware under the name "Siele", the private yacht of John H. French. In 1936 she was sold to Robert H. Wolfe, of Columbus, Ohio, and renamed "Seawolf". "Seawolf" was bought by the Navy on 13 January 1941, and commissioned on 9 April 1941, Lieutenant G. A. Lange in command. She was