A matrix of Galena with dark red transparent Rhodonite crystals throughout. A classic mineral & location, an essential for any Aussie collection. The specimen is mounted on perspex to go straight into your cabinet.
5.7cm x 6.2cm x 2.7cm, 212g.
Broken Hill, NSW, Australia.
RHODONITE GALENA CRYSTALS
Rhodonite is an attractive mineral, often carved and used in jewelry. Named in 1819 by Christoph Friedrich Jasche from the Greek “rhodon” or “rhodos” meaning “rose”, referring to its colour. Rhodonite does not react to acids. It is usually associated with black Manganese minerals, Galena and Pyrite.
Color is typically pink to red or orange and even black.
Luster is vitreous to dull to pearly on polished surfaces.
Transparency: Crystals are generally translucent and rarely transparent.
Crystal System is triclinic; bar 1
Crystal Habits include crystals that have a blocky prismatic habit, however crystals are rare. More typically massive, coarse and fine granular aggregates.
Cleavage is perfect in two directions forming prisms with a rectangular cross-section.
Fracture is conchoidal.
Hardness is 5.5 – 6.5.
Specific Gravity is approximately 3.4 – 3.7+ (above average for translucent minerals)
Streak is white.
Associated Minerals are calcite, pyrite, microcline, spessartine, pyroxmangite and other manganese minerals.
Other Characteristics: May tarnish to a brown or black color upon exposure until poslished.
Notable Occurrences include Ural Mountains, Russia; Broken Hill and Tamworth, Australia; Langban, Sweden, Menas Gerais, Brazil and Massachusetts and Franklin, New Jersey, USA.
Best Field Indicators are color, black inclusions, lack of reaction to acid and hardness.
Lead Sulfide PbS GALENA 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. 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.