Search Mineralpedia – A Mineral Photo Database and Identification Guide
Jahnsite - (NaFeMg) occurs in at the Tip Top pegmatite west of Custer, South Dakota. Thus far it has been a one-time find. Crystals occur as 1mm pseudo-orthorhombic twinned prisms to 1mm in tiny vugs within Heterosite with dark purple Leucophosphite and Dufrenite. The crystals are translucent yellow with orange bands near the termination. Two other new Jahnsites (NaMnMg) and (CaMgMg) are present in the crystals but can be characterized due to insufficient volumes.
Ref. Kampf, A.R., Steele, I. M., Loomis, T. A. Am.Min. 93,940-945(2008).
Named to honor Robert Jameson, the Scottish mineralogist who was the first to describe the mineral. Jamesonite is a relatively common mineral with numerous localities including in England, Germany, the Czech Republic, Romania, Bolivia, Mexico, the United States, and China, which are all known for rich material. Jamesonite forms as a late stage mineral in lead-silver-zinc veins that formed at low to medium temperatures. Associated minerals include other lead sulfosalts, pyrite, sphalerite, galena, tetrahedrite, stibnite, quartz, siderite, calcite, dolomite, and rhodochrosite.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/jamesonite.pdf
Named for Jan Haug, an amateur mineralogist who was the first to observe the mineral. Janhaugite occurs in groundmass and crystal lined cavities in sodium- rich granites. It is a rare mineral that can be found only in Norway at its type locality at Gjerdingselva and in the Khibiny Massif in the Kola Peninsual of Russia. Associated minerals include pyrophanite, elpidite, monazite, dalyite, and kupletskite.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/janhaugite.pdf