Mineral of the Month: May 2014
Color is red to pink, sometimes almost white, yellow and brown.
Luster is vitreous to resinous.
Transparency: Crystals are transparent to translucent.
Crystal System is trigonal; bar 3 2/m.
Crystal Habits include the rhombohedrons and scalahedrons with rounded or curved faces that can obscure the crystal shape. Some crystals can be flattened to a bladed habit and these are sometimes aggregated into rosettes or minute crystals into spherules. Also botryoidal, globular, stalactitic, layered, nodular, vein-filling and granular.Twinning is somewhat common forming penetration twins and contact twins similar to calcite’s twins.
Cleavage is perfect in three directions forming rhombohedrons.
Fracture is uneven.
Hardness is 3.5 – 4.
Specific Gravity is approximately 3.5 (above average)
Streak is white.
Other Characteristics: Pink and white banding in massive forms, non-fluorescence and specimens effervesce easily with dilute acids.
Associated Minerals include calcite, ankerite, alabandite, rhodonite, bementite, spessartine, fluorite, manganite, quartz and many metal sulfides.
Notable Occurrences are numerous and include the famous Sweet Home Mine, Alma, Park County and American Tunnel, Silverton, Colorado; Butte, Montana; the mines of Franklin, New Jersey; Humboldt Mine, Cochise County, Arizona and many sites in California, USA. Also found in Catamarca, Argentine; Huaron Mine and several mines in Ancash Department, Peru; Kara oba, Kazakhatan; Sacrimb, Transylvania, Romania; Cornwall, England; Harz Mountains, Germany; Tsumeb, Otavi, Namibia; Santa Eulalia and Magdalena, Mexico; N’Chwanging Mine, Hotazel, South Africa; Mont Saint-Hilaire, Quebec, Canada and many other localities from around the world.
Best Field Indicators are color, crystal habit, reaction to acid, non-fluorescence and perfect cleavage.
Sweet Home Mine (Home Sweet Home Mine), Mount Bross, Alma District, Park Co., Colorado, USA
Largest known crystal, 14cm x 16.5cm, from the Sweet Home Mine near Alma, Colorado.
Pink form of rhodochrosite from Silverton, Colorado
Cross section of rhodochrosite stalactite from LaPlata, Argentina.
The Searchlight rhodochrosite crystal, a large one from Alma, Colorado. Named for the area in which it was found.