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Named for the Arabic rahj al ghar, meaning “powder of the mine,” likely in allusion to its sometimes powdery form. Relatively common, fine crystals come from localities including, Germany, Switzerland, Romania, the Czech Republic, Macedonia, Russia, Japan, China, and the USA. Realgar commonly occurs in hydrothermal veins of low temperature usually associates with other arsenic minerals or antimony minerals. It can also occur as a volcanic sublimation as well as in hot springs and can also be found in carbonate and clay sedimentary deposits. Upon exposure to light for long periods, Realgar will disintegrate to a powder.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/realgar.pdf


Named for its type locality near Redding Township in Connecticut, USA. Reddingite is a rare mineral found in only a few localities including, additionally, Poland, Germany, and notably large crystals from Brazil. It forms as a secondary mineral as the product of hydrothermal alteration in granite pegmatites.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/reddingite.pdf


Named for the first noted occurrence at the Red Gill mine in Cumbria, England, however the type locality is listed as the Silver Gill. Redgillite occurs as translucent to transparent grass-green bladed crystals, generally in radiating groups.  It is found in thin fractures in oxidized sulfides, and is associated with langite, malachite, cuprite, connellite, and brochantite.

Ref. Pluth, J. J., et al. and Mineralogical Magazine December 2005 v. 69 no. 6 p. 973-980


Named after its type locality at the Red Ledge mine in California. Redledgeite is a rare mineral that occurs on chrome ores in gold deposits at the Red Ledge locality. May also have Italian and Russian localities.  Redledgeite is associated with chromite, chromian clinochlore and knorringite.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/redledgeite.pdf


Named for Frank S. Reed and John L. Mergner who were petrographic technicians at the United States Geological Survey.  Found at only three localitites, Reedmergnerite occurs in crystals parallel to bedding laminations in dolomite rock and oil shales, and also in pegmatites. Localities include the type locality at the Joseph Smith No. 1 well in Utah and at Wind Mountain in New Mexico in the USA, at the Dara-i-Pioz massif in Tajikistan, and from the Lovozero massif in Russia.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/reedmergnerite.pdf

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