From the Stone Age to the Millenial Generation: Gemstones. Stone jewellery, often known as gemstones, has a unique position in the world of fashion. Natural gemstones come in around 200 distinct kinds. Gemstones are both precious and semi-precious stones. The four most valuable gemstones are diamond, emerald, sapphire, and ruby. The list of semi-precious gemstones includes all other gemstones....