BASALT

Basalt is one of the most widely distributed rocks on earth. It is formed from molten lava which has solidified and is classed as an extrusive igneous rock. It makes up 90% of all igneous rocks on earth.

It is black when extracted but may change colour when in contact with the atmosphere. It contains quartz, feldspar, pyroxenes and olivene and has fine grains. It is similar in composition to gabbro although this has much larger, coarser grains. It is also closely related to andesite, but basalt is darker in colour.

Basalt makes up Giant's Causeway in Northern Ireland and Fingals Cave (Scotland). It may also be found particularly in Australia and Germany and on the moon (although specimens found here do not change colour because there is no atmosphere).

BERYL

Beryl is a silicate containing aluminium and beryllium and is very hard (7-8 on the mohs scale) and light. As it's colour varies it has many gemstone varieties such as emerald (green), heliodor (yellow) and aquamarine (blue). Small crystals may resemble apatite, although beryl is harder.

As well as being very popular as a gemstone, it is also used to produce beryllium which is a light, corrosive resistant metal used widely in the nuclear industry.

It is very widespread and forms in pegmatite rocks (rocks created by volcanic activity) and hydrothermals. Since it is very hard it is resistant to chemical alteration.

It is very widespread and can be found in very large samples in places such as Brazil, Columbia, India, Madagascar and South Africa.