KUTNOHORITE



Kutnahorite is a calcium manganese carbonate mineral. Numerous unpublished analyses by [Dunn] of specimens from both Franklin and Sterling Hill, show minimal substitution of Fe, Mg, and Zn in kutnahorite; values for FeO, MgO, and ZnO are all < 1.2 wt. %. Mucci (1991) obtained slightly higher values for one specimen. Some of the samples of Frondel and Bauer were further examined by J. R. Goldsmith and others who reported them to be two-carbonate assemblages, one of the phases having a near-kutnahorite composition with "several percent of Mg" and the other to be Ca-rich or Mn-rich, suggesting a solvus in the Ca-rich as well as in the Mn-rich area of the phase diagram (Goldsmith, 1959, 1983).
Although originally known from Czechoslovakia, the status of kutnahorite was unsettled until the definitive study of Frondel and Bauer (1955). The name roepperite was used by Kenngott (Brush, 1872a, 1872b) for the manganesian dolomite earlier reported by Roepper (1870), but the name was not accepted inasmuch as roepperite had previously been assigned to what is now fayalite. Additional data were given by Huang and Kerr (1960) and Cook (1973). The crystal structure was studied by Peacor et al. (1987a) who found Sterling Hill kutnahorite to be highly ordered. The free energy of formation of Sterling Hill kutnahorite at 25° C and one atmosphere total pressure is -1981.8 kJ mol-1 according to Mucci (1991), who also studied its solubility. See also Boettcher et al. (1992).
Kutnahorite occurs as massive and granular material in veins; the color is almost always some shade of pink, although highly calcian material may be nearly white. The luster is vitreous; the rhombohedral cleavage is well-developed; cleavage surfaces are commonly curved; and large masses of coarsely-crystallized material are known. The density is 3.12-3.14 g/cm3. Indices of refraction, varying substantially, were given by Cook (1973) and Huang and Kerr (1960).
Kutnahorite is, according to Frondel (1972), the most common member of the dolomite group at Franklin and Sterling Hill, but is more abundant at Sterling Hill. [Dunn] suggests dolomite is much more abundant. The Franklin kutnahorite studied by Frondel and Bauer (1955) occurred as anhedral masses up to 3 cm in size in a vein in franklinite ore. Sterling Hill kutnahorite also occurs in seams in franklinite ore, is commonly associated with willemite, and occurs in masses weighing many kilograms. (Dunn, 1995)

 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1901
     
 Formula: Ca(Mn,Mg,Fe)(CO3)2
 Essential Elements: Calcium, Carbon, Manganese, Oxygen
 All Elements in Formula: Calcium, Carbon, Iron, Magnesium, Manganese, Oxygen
     
 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   Kutnohorite

     
 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.617

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.64
The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 33, No. 1 - Spring 1992, pg. 24Research Reports Kutnahorite
View IssueV. 30, No, 2 - Fall 1989, pg. 17Research Reports, Kutnahorite
View IssueV. 18, No. 1 - March 1977, pg. 9The Post Palache Minerals - Kutnahorite
View IssueV. 7, No. 2 - August 1966, pg. 10The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Kutnahorite
View IssueV. 6, No. 2 - August 1965, pg. 11Kutnahorite (small article)
View IssueV. 6, No. 1 - February 1965, pg. 8Kutnahorite (small article)
View IssueV. 2, No. 2 - September 1961, pg. 9Kutnahorite - A Manganese Dolomite by Clifford Frondel an L. H. Bauer, Dept. of .Mineralogy, Harvard University, Cambridge, Mass, and New Jersey Zinc Company, Franklin, New Jersey.
     
Images
     
Kutnohorite, pink willemite inclusions and franklinite, Sterling Hill Mine, Ogdensburg, NJKutnohorite, pink willemite inclusions and franklinite, Sterling Hill Mine, Ogdensburg, NJ under shortwave UV Light
Kutnohorite (pinkish white), pink willemite inclusions and franklinite from Sterling Hill Mine, Ogdensburg, NJ. Photo by WP.
Kutnohorite, pink willemite inclusions and franklinite from Sterling Hill Mine, Ogdensburg, NJ under Shortwave UV light. The kutnohorite and franklinite is non-fluorescent, the willemite fluoresces green. Photo by WP.

Kutnohorite with willemite crystal and minor franklinite from the Sterling Hill Mine, Ogdensburg, NJKutnohorite with willemite crystal and minor franklinite from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV Light
Kutnohorite (pink) with willemite crystal and minor franklinite (black) from the Sterling Hill Mine, Ogdensburg, NJ. 8" x 6". From the collection of, and photo by, JVF.
Kutnohorite with willemite crystal and minor franklinite from the Sterling Hill Mine, Ogdensburg, NJ under shortwave UV light. The willemite fluoresces green, franklinite and kutnohorite are non-fluorescent. 8" x 6". From the collection of, and photo by, JVF.






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