Dolomite



Dolomite is a calcium magnesium carbonate mineral. The only published analysis is by Yau et al. (1984) who gave the composition of a specimen associated with margarite in the Franklin Marble as (Ca0.49Mg0.48Mn0.1Fe0.2)2(CO3)2. The paucity of analytical data precludes general statements about solid solution towards ankerite, minrecordite, and kutnahorite. Compositional data given herein under kutnahorite suggest very little Mg-Mn solid solution in the specimens studied to date. However, as noted by Frondel (1972), Mn is to be expected in the as-yet unstudied orebody dolomites.
Dolomite is a common mineral at Franklin and Sterling Hill. It is also found in the Franklin Marble. Much dolomite is probably unrecognized as such. It was first identified by Palache (1929, 1935) but has been little studied. The manganesian dolomite of Roepper (1870) is likely kutnahorite.
Much local dolomite is massive, white to gray, gray-brown, and nondescript in appearance. Small (< 1 cm) crystals are common in vein assemblages and are commonly curved and/or saddle-shaped. A slightly pearly vitreous luster is common, and the rhombohedral cleavage is well developed. No physical or optical data exist.
Dolomite was present as the major constituent of a small geologic feature, perhaps formed in part by replacement, and known as the "Buckwheat Dolomite". This was found in a large vein-like mass in the west wall of the Buckwheat Open Cut. It was mostly removed in the overburden-stripping process, and much of it was deposited on the now-named Buckwheat Dump. This dolomite is well known to collectors of micromounts, because it is very vuggy, and at least eighteen well-crystallized mineral species have been reported from its vugs, as noted and illustrated by Peters et al. (1983). This adds yet another mineralogical dimension to Franklin.
Dolomite plays a considerable role in late veins in the Franklin orebody. These are referred to as "carbonate veins" in the willemite discussion and consist of willemite (commonly of radial habit) with serpentine and calcite and, locally, with rhodochrosite and talc. Dolomite forms part of the outside contact edges of such veins, which commonly crosscut the bedding of the ores and are thought to be Paleozoic in age. Additionally, in other, perhaps genetically related assemblages, dolomite is associated with a number of other minerals, such as calcite, hematite, sphalerite, lennilenapeite, and magnesioriebeckite.
The occurrence of dolomite at Sterling Hill is less well represented in the specimen collections available for study. Given the abundance of Mg at Sterling Hill, dolomite is likely much more common than has been recognized. It has been found in carbonate veins similar to those from Franklin, but thinner and less abundant. Large amounts of dolomite are known from the north orebody and areas affected by the introduction of Mg-bearing solutions along the Zero fault. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
     
 Formula: CaMg(CO3)2
 Essential Elements: Calcium, Carbon, Magnesium, Oxygen
 All Elements in Formula: Calcium, Carbon, Magnesium, Oxygen
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Moderately bright to very weak red
 Mid wave UV light: Moderate to very weak red
 Longwave UV light: Moderate to very weak red
 Additional Information: Phosphoresces moderately bright to very weak red, fluoresces weakest longwave
     
 To find out more about this mineral at minDat's website, follow this link   Dolomite

     
 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.616

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.54


The Picking Table References
 PT Issue and PageDescription / Comment
V. 57, No. 2 - Fall 2016, pg. 16Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Dolomite
View IssueV. 41, No. 1 - Spring 2000, pg. 8Fluorescent Dolomite from Franklin and Sterling Hill Richard Bostwick
View IssueV. 29, No. 2 - Fall 1988, pg. 4The Buckwheat Dolomite Fissure Mineralization of Paleozoic Age
View IssueV. 27 No. 2 - Fall 1986, pg. 5Minerals of the Franklin Quarry, Philip P. Betancourt, Dolomite
View IssueV. 24 No. 2 - Fall 1983, pg. 13Minerals of the Buckwheat Dolomite Franklin, New Jersey, Dolomite (small description)
     
Images

     
Dolomite from Franklin, NJ.  Non-fluorescent.
Dolomite from Franklin, NJ. Non-fluorescent. Photo by JVF.







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