GALENA Lead Sulfide PbS
GALENA Lead Sulfide PbS is a common and popular mineral for rock hounds. Its characteristic cubes, distinctive cleavage and high density make it easy to identify and a favorite in high school geology labs. The structure of Galena is identical to that of halite, NaCl. The two minerals have the same crystal shapes, symmetry and cleavage. Some Galena may contain up to 20% silver. Galena is the leading ore of Silver.
Is the primary ore mineral of lead. Worked for its lead content as early as 3000 BC, it is found in ore veins with sphalerite, pyrite, chalcopyrite, tennantite-tetrahedrite, etc. and in skarns, as well as in sedimentary rocks where it may replace carbonate beds or be deposited in pore spaces. The crystals are bright when fresh but often tarnish after exposure to air and especially when people touch it. Lead sulfide may contain impurities, such as silver, arsenic, antimony, and copper.
One of the first transistors was a Galena Crystal and with a copper wire called “cats-whisker-with crystal”. Galena is a natural semiconductor. Really it formed part of a transistor, a more reliable PN junction or Diode. Metal Sulfides were experimented with in the late 1800s and early 1900s as they form natural PN Junctions like copper and copper oxide (Verde or Patina) which also formed one of the first solar panels. Such an interesting subject I could on on about it.
There are many forms of Galena specimens. Cubic Crystal, Octahedron Crystal, Cuboctahedron or Octacube, Truncated, Skeletal, Melted, Wet look and more.
Color is lead to silver gray sometimes with a bluish tint.
Luster is metallic to dull in weathered faces.
Transparency crystals are opaque.
Crystal System is isometric; 4/m bar 3 2/m
Crystal Habits include the cube, octahedron and combinations of the two. Spinel twinning is possible forming flattened crystals. Also massive and granular.
Cleavage is perfect in four direction forming cubes.
Fracture is uneven and rarely seen because of the perfect cleavage.
Hardness is 2.5+
Specific Gravity is approximately 7.5+ (heavy even for metallic minerals)
Streak is lead gray
Chemistry PbS, Lead Sulfide
Uses Major ore of lead and silver, Specimens, previously Plumbing pipes and Paint. It is toxic when ingested or inhaled.
Brighter metallic luster on cleavage surfaces than on crystal faces.
Notable occurrences include Texas-Oklahoma-Missouri area, USA; Germany, Peru, Mexico, Zambia, and England.
Best Field Indicators are crystal habit, cleavage and, perhaps most importantly, density.
Associated Minerals are Cerussite, Anglesite, Quartz, Sphalerite, Chalcopyrite, Pyrite, Bornite, Barite, Siderite, Dolomite, Calcite, Marcasite, Fluorite and then some.