What are gemstones? When we speak of gemstones, we usually mean
minerals that have been cut and polished. However, over the
ages, humans have used a great variety of materials for
decoration. Minerals have been cut and polished, and organic
materials like coral, pearls, amber and ivory have been
fashioned. Small fossils are often set in jewellery. Widespread
materials like horn, bone, shells, seeds, even wood abound, as
well as made materials like glass and pottery. Not all minerals
are suitable for gemstones. As well as beauty, a mineral must
possess hardness and stability, and occur in crystals or masses
large enough for cutting. Such material is very rare. Many
minerals are small, opaque or easily damaged. Of over 4000 known
minerals, only about 100 minerals are ever worked and only about
20 are commonly used in jewellery. A number of opaque minerals
and rocks with attractive colours and patterns are polished to
make beads, carvings, bowls and decorative items. Such minerals
are broadly termed 'ornamentals