Caryopilite is a manganese silicate hydroxide mineral. Microprobe analyses of several caryopilites the variability of its composition.
Contrary to the usual local relations, Franklin caryopilite is much more magnesian than that from Sterling Hill. The analysis of Sterling Hill material is of the rosette-grouped crystals illustrated here. Dunn et al. (1981c) calculated these analyses on the basis of 8 octahedral cations, but it has been shown by Guggenheim et al. (1982) that such data are best calculated on the basis of a serpentine-like formula with octahedral cations to silicon = 9:6. The role of As in caryopilite is uninvestigated to date.
Caryopilite was first described from Franklin and Sterling Hill by Dunn et al. (1981c). It has been little studied since and, as noted by Guggenheim et al. (1982), it may be a component of some bementite.
Franklin caryopilite is dark reddish brown, massive, and fine-grained; hand-sized specimens are known. Sterling Hill caryopilite occurs in rosettes of pseudohexagonal, 1 mm, platy crystals, which have a brownish-orange color. No measurements of physical or optical properties have been made. There is no discernible fluorescence in ultraviolet. It is best distinguished using X-ray methods.
The studied Franklin caryopilite occurs in a distinctive, dark reddish-brown, massive intergrowth with calcite, on calcite-willemite-franklinite ore. There are several generations each of calcite and caryopilite, grown en echelon. Fine crystals of allactite occurs within interstices in the caryopilite-calcite matrix.
Caryopilite also occurs in small amounts as reddish to pink or brown hemispherules, nodular masses, and clumps, commonly on rhodonite. A caryopilite-like mineral also occurs as a replacement of barite, and a caryopilite-like mineral was observed in the original baumite assemblage by Guggenheim and Bailey (1989).
The studied Sterling Hill caryopilite occurs as distinctive rosettes associated with secondary growths of willemite, calcite, sphalerite, and franklinite, on willemite-franklinite-calcite ore.
There may be a number of unrecognized caryopilite occurrences at both Franklin and Sterling Hill. (Dunn, 1995)

 Location Found: Franklin and Ogdensburg
 Year Discovered: 1889
 Formula: (Mn,Mg)3(Si2O5)(OH)4
 Essential Elements: Hydrogen, Manganese, Oxygen, Silicon
 All Elements in Formula: Hydrogen, Magnesium, Manganese, Oxygen, Silicon
 IMA Status: Approved
 To find out more about this mineral at minDat's website, follow this link   Caryopilite

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.490

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 23, No. 1 - Spring 1982, pg. 10Mineral Notes Research Reports, Caryopilite
View IssueV. 23, No. 1 - Spring 1982, pg. 11Additional Information on Schallerite and Friedelite and Caryopilite, Pete J. Dunn

Caryopilite, franklinite, willemite, calcite and chlorophoenicite crystals from the Sterling Hill Mine
Caryopilite (brown), franklinite (black), willemite (red-brown), calcite (white) and chlorophoenicite crystals (white needles) from the Sterling Hill Mine, Ogdensburg, NJ. Field of view 13/16" (20mm). From the collection of Mark Dahlman, photo by WP.

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