Pyrosmalite-(Mn)



Manganpyrosmalite (Pyrosmalite-(Mn)) is a manganese silicate hydroxide chloride mineral of the friedelite group and is polymorphous with friedelite. Several unpublished analyses of specimens from this assemblage indicate that the composition of this material varies only slightly. The data for local material show extensive substitution of Fe for Mn in manganpyrosmalite, as compared with friedelite, in which such solid solution is quite limited. An analogous relation is seen in schallerite and nelenite, wherein nelenite is receptive to much Fe substitution for Mn, and schallerite is not.
Manganpyrosmalite was first described as a new species from Sterling Hill by Frondel and Bauer (1953), and the formula was further discussed by Hey (1956). It has been found sporadically since, but only at Sterling Hill. One occurrence was described by Parker and Guy (1990), but most of the occurrences remain largely unstudied. Some specimens may be mislabeled as friedelite in older collections.
Manganpyrosmalite occurs as both massive material and as fine euhedral crystals which are composed of prisms, pinacoids, and pyramids. Such crystals may be randomly intergrown or may exhibit strong columnar parallel growth. Massive manganpyrosmalite is distinctly brown to yellow-brown in all specimens seen by [Dunn], except for slightly altered material; hand-sized masses are known. Massive, fine-grained aggregates have a decidedly dull to very slightly bronzy to resinous luster, and a distinct, radial fibrosity may be readily apparent on polished surfaces.
Euhedral crystals are slightly brownish pink and faintly colored. The luster is vitreous on cleavage surfaces and crystal faces. The density is 3.13 g/cm3, and cleavage is perfect. There is no discernible fluorescence in ultraviolet. It is best distinguished from friedelite, nelenite, and schallerite using X-ray methods.
The type manganpyrosmalite consists of large 10-15 cm specimens of brown, platy to tight-fibrous masses which have inclusions of franklinite and calcite sparsely distributed within them. Little is known of the occurrence of this assemblage, although one of Lawson Bauer's specimens lists "black willemite" as an associated mineral. This would be consistent with the anomalously high iron content, inasmuch as there was high Fe-silicate activity associated with the black-willemite, fayalite, and loellingite assemblage.
Superb crystals were found in 1980 on the 1400 level of Sterling Hill. They were found in a 25-cm pod associated with calcite, diopside, amphibole, and sphalerite (Parker and Guy, 1990) and are the best manganpyrosmalite crystals found here. Additional occurrences have also been noted at Sterling Hill, intimately mixed with friedelite. Among them are: (1) manganpyrosmalite with willemite, friedelite, calcite, and chlorite from the 1010 stope; (2) manganpyrosmalite with friedelite and a Mn-carbonate from the 1500 level; and (3) very light brown, extremely fine-grained, manganpyrosmalite with friedelite, calcite, and franklinite, from the 1100 level. (Dunn, 1995)


 Location Found: Ogdensburg (Type Locality)
     
 Mineral Note: Originally named manganpyrosmalite by By Clifford Frondel and Lawson H. Bauer for its manganese-dominant composition relative to the original pyrosmalite.
 Year Discovered: 1953
     
 Formula: (Mn,Fe)8Si6O15(OH,Cl)10
 Essential Elements: Hydrogen, Manganese, Oxygen, Silicon
 All Elements in Formula: Chlorine, Hydrogen, Iron, Manganese, Oxygen, Silicon
     
 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   Pyrosmalite-(Mn)

     
 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.478. 'Manganpyrosmalite'

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.67


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 31, No. 1 - Spring 1990, pg. 6Manganpyrosmalite Crystals From Ogdensburg, New Jersey (Originally named By Clifford Frondel and Lawson H. Bauer, renamed Pyrosmalite-(Mn))
View IssueV. 18, No. 1 - March 1977, pg. 10The Post Palache Minerals - Manganpyrosmalite now Pyrosmalite-(Mn)
View IssueV. 9, No. 1 - February 1968, pg. 15The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Manganpyrosmalite (Short Note)
     
Images

     
Pyrosmalite-(Mn) crystals on calcite, Sterling Hill Mine, Ogdensburg, NJ
Pyrosmalite-(Mn) crystals (pinkish brown) on calcite (white) from the Sterling Hill Mine, Ogdensburg, NJ. Field of view 2 mm. From the collection of, and photo by DW.







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