Chondrodite



Chondrodite is a magnesium silicate fluorine hydroxide mineral of the humite group. In the marble, Fe is the major substituent, whereas in the Sterling Hill orebody Mn and Zn are common substituents. Local material has been much studied. The best of these studies are those of Sahama (1953) and Jones (1969), who addressed the OH/F ratios in local material.
Chondrodite was first described locally by the name maclureite (Seybert, 1822). The name brucite was applied early to such material (Gibbs, 1819).
Local chondrodite occurs as both euhedral crystals and as subhedral grains and masses up to 10 cm in size. The euhedral crystals, up to 1 cm in size, may have been known to Palache in 1935, but have not been measured or figured. The bulk of local chondrodite is brown to orange-brown to yellow. The luster is vitreous; cleavage is poor; and the density is 3.260 g/cm3. The fluorescence in ultraviolet, for chemically studied samples, is somewhat variable: most specimens fluoresce orange, with slightly more intensity in shortwave than longwave. This variation may be due to the presence of Fe substituting for Mg. Chondrodite is best differentiated from norbergite and other humites using X-ray diffraction methods.
Chondrodite is common as irregular segregations, isolated crystals, and masses and is likely a very common mineral throughout the Franklin Marble. It is associated with spinel, pyrrhotite, graphite, and other minerals and was found on the Buckwheat Dump by Cook (1973). Larsen et al. (1928) noted that chondrodite formed the cores of some norbergite crystals. [Dunn’s] studies do not support the statements by Larsen et al. (1928) and Cook (1973) that most of the known local specimens labeled chondrodite are norbergite. The distinctly brown to orange-brown material is mostly chondrodite, an observation also supported by Kearns (1977) for specimens from the northern parts of the Franklin Marble in New York.
At Sterling Hill, manganoan chondrodite was found as massive material with calcite, franklinite, and zincite and is also found in coexistence with unanalyzed but presumably manganoan humite. Other Sterling Hill occurrences include one with arsenopyrite and calcite on the 900 level and one with calcite and mica on the 1500 level. (Dunn, 1995)


 Location Found: Franklin
     
 
 Year Discovered: 1817
     
 Formula: (Mg,Fe2+)5(SiO4)2(F,OH)2
 Essential Elements: Fluorine, Magnesium, Oxygen, Silicon
 All Elements in Formula: Fluorine, Hydrogen, Iron, Magnesium, Oxygen, Silicon
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
Fluorescent Mineral Properties

 Shortwave UV light: Bright to weak yellow to orange-yellow to yellow-orange
     
 To find out more about this mineral at minDat's website, follow this link   Chondrodite

     
 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.346

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.50


The Picking Table References
 PT Issue and PageDescription / Comment
V. 57, No. 2 - Fall 2016, pg. 15Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Chondrodite
View IssueV. 33, No. 2 - Fall 1992, pg. 10The Check List of Franklin-Sterling Hill Fluorescent Minerals - Chondrodite (Fluorescent Info)
View IssueV. 18, No. 1 - March 1977, pg. 22The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Chondrodite
View IssueV. 13, No. 2 - August 1972, pg. 12The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Chondrodite/Norbergite (Fluorescent Info)
     
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