RAMMELSBERGITE



Rammelsbergite is a nickel arsenide mineral of the loellingite group. The analysis of chloanthite by Koenig (1890) may have been of impure rammelsbergite.
Rammelsbergite, together with gersdorffite and loellingite, comprise the bulk of the opaque minerals associated with nickeline at Franklin and were first noted, as chloanthite, by Koenig (1889, 1890). The assemblage is described in detail under nickeline. Rammelsbergite subsequently was shown to occur here by Holmes (1935, 1936, 1945, and 1947), who used the term "white arsenides" to describe the predominant rammelsbergite-gersdorffite mixture. It is not known from Sterling Hill.
Rammelsbergite is silver-white to silver-gray, opaque, and has metallic luster. Crystals, if discernible, are modified pseudo-octahedrons. Surfaces are commonly dull, perhaps due to alteration of associated gersdorffite. Aggregates are bulbous in part, representing the outermost section of a cauliflower-like termination of an arborescent dendrite. It is easily confused with loellingite, with which it is isostructural and associated, and with arsenopyrite; it requires chemical or X-ray verification.
Rammelsbergite occurs intimately associated with nickeline, gersdorffite, loellingite, and other species as dendrites, which were described in substantial detail by Oen et al. (1984). In general, rammelsbergite, sometimes intimately associated with gersdorffite in concentric aggregates, coats the trunks of arborescent nickeline dendrites and forms the uppermost part of such dendrites. Remnant nickeline is sometimes seen at the cores of such aggregates.
The gangue minerals are sphalerite, fluorite, calcite, barite, and rarely ferrostilpnomelane. Masses of rammelsbergite with gersdorffite have been found in which the dendritic habit is not evident. See the discussion under nickeline. (Dunn, 1995)

 Location Found: Franklin
     
 
 Year Discovered: 1854
     
 Formula: NiAs2
 Essential Elements: Arsenic, Nickel
 All Elements in Formula: Arsenic, Nickel
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
     
 To find out more about this mineral at minDat's website, follow this link   Rammelsbergite

     
 References:
Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.551

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.73
The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 31, No. 1 - Spring 1990, pg. 3Breithauptite From The Nickel-Arsenide Assemblage at Franklin, New Jersey, Rammelsbergite (small description)
     
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