A precious gem is nature's wonder, beautiful, valuable, brightly
coloured and extremely rare.Crystalline precious stones including
popular gems such as ruby, emerald, sapphire, tourmaline, spinel,
aquamarine, tanzanite and amethyst. Other gemstones in the broadest
sense of the word, include pearls, opals, rose quartz and prehnite,
which are also used in jewellery.