List of stones

Marble is limestone that has been changed from a sedimentary rock to a crystalline one through high pressures under the surface of the Earth. Marble is much stronger than limestone, and can be polished to a shiny finish. It is frequently used for making statues from, and for making decorative features in buildings like floors and pillars from.

Moonstone is a mineral made from potassium aluminium silicate. It is formed in thin layers, which gives it an interesting light scattering effect called adularescence. The highest quality moonstones come from Sri Lanka.

Olivine is a common olive green mineral made up of magnesium iron silicate. It has also been found in asteroids and on the moon. Olivine can be quite brittle. When olivine is transparent and gem quality, is is called peridot.

Opal is not a true mineral, but a crystalline gel made up of spheres of silicon dioxide and water. The pattern of the spheres makes opal refract light into lots of different colours, with blue and green being the most common. Opal is used often in jewelry, and is the national stone of Australia.

Pearls are made inside the shells of mollusks like clams and oysters. They are usually round, and have a soft, translucent glow to them. Pearls have been made into jewellery for thousands of years.