Rocks and Minerals Information Sheet R008
This is a very interesting and heavy ore of Zinc. It is also sometimes referred to as Zinc-Blende, Black-Jack, and Schalenblende. The primary constituent is Zinc Sulphide combined with Iron. The amount of Iron affects the colour but generally Sphalerite specimens are yellowy-brown and greyish-black.
The pale yellow, purer Sphalerite, is known as Cleiophene and as Iron content increases it forms dark opaque metallic crystals known as Marmatite (not to be confused with a well know spread of a similar name! ).
Sphalerite forms in hydrothermal veins often with Galena and other sulphides. It is not always easy to recognise due to its variations in colour, indeed the name is derived from the Greek word for "treacherous". It is also often associated with Pyrite and Magnetite.
The polished egg featured on the
is fascinating with metallic shine and very heavy for its size.
Zinc is the fourth most common metal in use today and the majority is extracted from Spahlerite, which used to be mined in France and Germany - the main industrial sources of Sphalerite are now China, Australia and Peru.