Gersdorffite is a nickel arsenic sulfide mineral. Fe and Co substitute for nickel. Gersdorffite was originally reported from Franklin by Holmes (1945) and likely comprised a small part of the material referred to as chloanthite by Koenig (1889) and Palache (1935). It is not known from Sterling Hill and is a rare mineral locally.
Gersdorffite is gray, opaque, and very fine-grained. It occurs in bands up to 0.5 cm in width, but is not easily discernible from rammelsbergite without optical or X-ray technique.
At Franklin, gersdorffite occurs in the nickel-arsenide assemblage, found but once, most recently described by Oen et al. (1984). Gersdorffite occurs as a part of dendrites which have general growth sequences (toward the exterior) of nickeline → rammelsbergite → gersdorffite → nickel-rich loellingite. Several generations of gersdorffite are present in some specimens, with the outermost zone being richer in Fe and Co than the more nickel-rich inner zones. (Dunn, 1995)

 Location Found: Franklin
 Year Discovered: 1845
 Formula: NiAsS
 Essential Elements: Arsenic, Nickel, Sulfur
 All Elements in Formula: Arsenic, Nickel, Sulfur
 IMA Status: Approved
 To find out more about this mineral at minDat's website, follow this link   Gersdorffite

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.533

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.58

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, Gersdorffite (small description)
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