A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires.
The Guinness Book of World Records names Painite as the rarest gem mineral on earth. Painite has so far only been found in Myanmar, Indonesia. Colours vary from pink to brown and like diamond, Painite will appear a different colour when viewed from different angles. Very few Painite crystals are known to exist and even fewer have been cut into gemstones.