GALENA

A sulphide which is grey in colour and is the main industrial source of lead. The name galena is the Latin word for lead ore. It is also known as lead glance.

Lead is soft, dense, heavy and a poor conductor of electricity. It is also very malleable and can be easily flattened into sheets. Most lead is used for batteries but it is also used for solder and ammunition. Lead is very poisonous. In recent years health problems have resulted in the UK when lead from old pipes has contaminated drinking water.

Galena is very common and widely distributed. It is found in hydrothermals and sedimentary rocks and also in dolomites and limestones. It reacts easily with oxygen to form cerusite, mimetite or pyromorphite.

It may be found in New South Wales, Australia, Germany, Sardinia and Missouri and Oklahoma (US). It may also be found in Derbyshire, Cornwall and Derbyshire (UK).

GROSSULAR GARNET

A silicate which is very variable in colour. It may be black, brown, green, orange, pink or red and has a glassy to greasy sheen. It may be classed as a neosilicate. These minerals contain silica molecules which are isolated from one another within their structure.

It is very hard (6-7.5 on the mohs scale) and is therefore used as an abrasive. It may also be used in jewellery. Garnets have a very complex chemical composition with the proportion of metals varying from specimen to specimen.

Grossular garnet was discovered in Siberia in the early 1800's. Grossular is derived from the Latin word grossukaria which means gooseberry and refers to the green colour of the first specimen identified.

It forms by contact metamorphism and can be found in limestone rocks that have reacted with hot molten rock (magmatic inclusions). It may also be found in some igneous rocks.

Grossular garnet can be found in Canada, Italy, Mexico, Pakistan and Switzerland. Hessonite (also known as cinnamon stone) is a brown variety of grossular garnet that comes from Sri Lanka and Tanzania. Vanadium is another variety from Kenya.