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
Dom Pedro aquamarine Dom Pedro aquamarine The Dom Pedro aquamarine is the world's largest cut aquamarine gem. It was cut from a crystal originally weighing approximately and measuring more than in length. The stone was mined in Pedra Azul, in the state of Minas Gerais in Brazil around 1980, and named after the Brazilian emperors Pedro I and Pedro II. The blue-green gemstone was cut by Bernd Munsteiner into an obelisk form weighing 10,363 carats. The finished dimensions measure tall by wide. The jewel was donated to the Smithsonian Institution by Jane Mitchell and Jeffery Bland. It is housed in the National Museum