Over 90% of gemstones are refined from naturally occurring minerals, formed via inorganic processes; the remaining 10% are organic gemstones, non-mineral material such as pearl, amber, coral and ivory, which are formed in living organisms. Although more than 4,000 types of minerals have been identified, less than 100 minerals can be refined into gemstones. Of these 100 types, only 20 types or so are gemstone-grade and traded on the international gemstone market.