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
Gemstone industry in Greenland gemstone ruby. The native inhabitants continued to assist the European explorers with their ruby exploration, leading them to some half dozen locations, spread out for over a hundred miles along the southwest shores of Greenland, known as the Kitaa Coast. Ruby and pink sapphire are the red and pink varieties of the mineral corundum, an aluminum-oxide mineral Al2O3. The pink/red colour is formed in corundum by adding the element chromium to its crystal structure. Spectroscopy of rubies from the Aappaluttoq occurrence in Greenland confirm the presence of chromium as well as showing absorption in the UV region indicating high Fe