Gems & minerals

A gem, or jewel, is a cut and polished precious or semi-precious stone that can be used to make jewelry.
A gem can also be used to describe something that stands out as being better than everything around it, as in "this figurine is the gem of her collection".

Jade is a green, ornamental stone that has been used to carve decorative items from for thousands of years. It is particularly popular among Chinese artisans.
Jade is largely made up of iron, calcium and magnesium. The more iron, the brighter the shade of green.

Jet, also called lignite, is not a true mineral or stone. It is fossilised decaying wood. The original structure of the wood can be seen in jet under a microscope.
Jet is black and has been used to make jewellery for many years. It was quite popular to make mourning jewellery, for wearing at funerals.

Lapis lazuli is a semi-precious stone that has a deep blue colour. It is not a single mineral like most gemstones, but a composite rock that often has patterns of other colours through it, like marble. It polishes very well and is used for jewelry as well as in mosaics or other decorative finishes on buildings.

Limestone is a rock made up of calcium carbonate. It is formed by sediments at the bottom of the sea compressing over time into rock. The calcium carbonate in limestone comes from thousands and thousands of shells of sea creatures.
Limestone is an ingredient of mortar, cement and toothpaste. The stone itself can be carved into statues or cut into blocks to make buildings out of.

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.