Amber is a gemstone formed through the fossilization of tree resin. Amber resin is not the same as typical tree sap. It is sourced specifically from the Pinus succinifera tree. The fossilization of amber can be traced back to the Tertiary period, meaning that amber stones formed approximately 50 million years ago. Since amber is formed from soft and sticky resin, amber often contains animal and plant inclusions; mostly mosquitoes and other insect species. Amber that developed in coal seams is often called 'resinite', and specimens sourced specifically from New Zealand coal seams are referred to as 'ambrite'. Amber is one of the few varieties of organic gemstones. The most common varieties of organic gems include amber, pearl, coral and ivory.