GERSTMANNITE



Gerstmannite is a manganese magnesium zinc silicate hydroxide mineral. Re-analysis of type gerstmannite by [Dunn] found 5.0 wt. % fluorine which was missed in the original study; it is presumed to be in substitution for (OH), comprising 0.7 of the 2.0 (OH,F). Analysis by DTA-EGA confirmed the presence of H2O.
Gerstmannite is a rare mineral from Sterling Hill and has not been found at Franklin. It was described by Moore and Araki (1977a).
Moore and Araki (1977a) provided the crystal structure. Simonov et al. (1978) pointed out a structural relationship to clinohedrite. The gerstmannite structure is based on oxygen cubic close-packing and is composed of [MnMgO3(OH)2] octahedral sheets linked to [ZnSiO4] tetrahedral sheets.
Gerstmannite is light pink to white and occurs as bunched, flattened sprays of radiating prismatic crystals, up to several cm in composite length. It is translucent to opaque, with vitreous luster, good cleavage, and a density of 3.68 g/cm3.
There is no discernible fluorescence in ultraviolet.
Gerstmannite is known from secondary vein occurrences. Moore and Araki (1977a) described the type gerstmannite as occurring on calcite-rich willemite/franklinite ore from Sterling Hill. They described this ore as coated with magnesian calcite, followed by a mixture of brown manganpyrosmalite and sphalerite. Calcite and gerstmannite coat this assemblage. They described a second sample occurring with apple-green willemite and pink magnesian alleghanyite. [Dunn] has identified impure fluoborite as white veins crosscutting gerstmannite. (Dunn, 1995)

 Location Found: Ogdensburg (Type Locality), unique to Franklin/Ogdensburg area
     
 
 Year Discovered: 1975
     
 Formula: MnMgZn(SiO4)(OH)2
 Essential Elements: Hydrogen, Magnesium, Manganese, Oxygen, Silicon, Zinc
 All Elements in Formula: Hydrogen, Magnesium, Manganese, Oxygen, Silicon, Zinc
     
 IMA Status: Approved 1975
     
Fluorescent Mineral Properties
 Longwave UV light: Weak dull olive-green
     
 To find out more about this mineral at minDat's website, follow this link   Gerstmannite

     
 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.369
The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 57, No. 2 - Fall 2016, pg. 18Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Gerstmannite
View IssueV. 37, No. 1 - Spring 1996, pg. 18Closest-Packed Mineral Structures of Franklin-Ogdensburg: Kepler's Gift of the Snowflake, Part two of two parts, Paul B. Moore - Gerstmannite
View IssueV. 18, No. 2 - September 1977, pg. 4New Minerals - Gerstmannite
View IssueV. 17, No. 1 - March 1976, pg. 7New Minerals - Gerstmannite (small article)
     
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