TOP GALENA SPECIMEN
Stunning Top Galena Specimen, very well formed and shiny. This is a really aesthetic piece with great shape, well formed crystals and glossy wet surfaces. The Crystals have formed Cubic shape with the corners missing forming a Cuboctahedron or Octacube. There is a small section of Truncated (stepped) Crystal Galena and a few small Quartz Crystals. There is some micro Pyrite Crystals on a few sides of the larger Galena Crystals. I suspect there is a higher Silver content which helps create these glossy Crystals, amazing. A superb specimen from a premier location. Difficult to photograph with high reflection. Start or add to your own metals collection.
5.8cm x 3.5cm x 3.8cm, 144g.
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.
Pyrite is the classic “Fool’s Gold”. There are other shiny brassy yellow minerals, but pyrite is by far the most common and the most often mistaken for gold. Whether it is the golden look or something else, pyrite is a favorite among rock collectors. It can have a beautiful luster and interesting crystals. Abundantly found in Earth’s crust, in almost every possible environment. In Plutonic, Volcanic, Sedimentary and Metamorphic rocks. Interestingly this Metal Sulfide has a vast number of forms and varieties. Disc form called Pyrite Sun, Spheres formed of hundreds of squares, Cubes of near perfect squares, Octahedral crystal form and crystal cluster forms.
The word Pyrite or Pyr means fire in Greek. It is piezoelectric which means when it is struck with metal or a hard rock it gives off sparks. This spark can start fires for cave men and cave women, shall we say cave people just in case. Pyrite was used as the strike on a gun to make the bullet fire in days of yore.
Bravoite is closely related but contains up to 20% nickel. Some mineral books treat it as a variety of pyrite. Pyrite is a polymorph of Marcasite, which means that it has the same chemistry, FeS2, as Marcasite; but a different structure and therefore different symmetry and crystal shapes. Pyrite is difficult to distinguish from Marcasite when a lack of clear indicators exists. It is Dimorphic with Marcasite.
Pyrite’s structure is analogous to galena’s structure with a formula of PbS. Galena though has a higher symmetry. The difference between the two is; The single sulfur of galena is replaced by a pair of sulfurs in pyrite. This sulfur pair are covalently bonded together in an elemental bond. This pair disrupts the four fold symmetry that a single atom of sulfur would have preserved. This gives pyrite a lower symmetry than galena. The spelling of Sulfur can be Sulphur.
Striated, Cubic, Octahedral, Pyritohedral sometimes occurring as Twins (penetration is more than 50%) or Stacked (penetration is less than 50%). There are compact granular aggregates, Concretions, mammillated and stalactitic nodules. It’s hard stuff between 6 to 6.5 and heavy at 5. Enough said for a short description, below are Pyrite Mineral Specimen Images.
Quartz is a fascinating common mineral, found in the Earth’s crust. If pure, quartz forms colourless, transparent hard crystals with a glass like luster. A significant component of many igneous, metamorphic and sedimentary rocks. Found in an abundant variety of formations and colors.
Polished Quartz was the most advanced technology thousands of years ago, used by the Assyrians. As a lens to focus light, could help start a fire for cooking. The Vikings could have used one of these to find the sun on a cloudy day. As a magnifying glass the ancients could see the stars too. Today it leads technology being the main component of transistors which make our computers work and solar panels.
The presence of trace elements gives an abundance of color range and crystal forms. Quartz is hard 7, light 2.65 and just adorable with an amazing shine when polished. No cleavage, characteristic conchoidal fracture and strongly piezoelectric and pyroelectric (interestingly except in Twins where the opposites cancel each other out).