The Probert Encyclopaedia of Rocks & Minerals

GALENA

Galena (lead sulphide) or galenite is virtually the only source of lead and an important ore of silver. It is found both in masses and crystallized in cubes, but sometimes in truncated octahedra and has the formulae PbS and a relative hardness of 3. It is a very common metallic mineral, its colour is bluish-grey, like lead, but brighter; its lustre metallic; texture foliated; fragments cubical; soft, but brittle. When found in veins that show a connection to igneous rocks, it is frequently found with silver minerals. Galena is also found in limestones either as veins or as a replacement deposit.
Galena effervesces with nitric and hydrochloric acids. For the most part it contains about 86.6 per cent of lead and 13.4 of sulphur, generally some silver, and also antimony, zinc, iron, and bismuth. Where the proportion of silver is high it is known as argentiferous galena, and worked with a view to the extraction of this metal. Galena occurs principally in the older or primary rocks, being found in England mainly in the Mountain Limestone (base of the Carboniferous formation). In the United States it is very abundant, the deposit of galena in which the mines of Illinois are situated being extensive and important.
Research Galena