Epidote



Epidote, a calcium iron aluminum silicate hydroxide mineral, is relatively rare at Franklin. Nuttall (1822) reported it as a laminated green mineral with garnet, and Palache (1935) reported it from the contacts of the ore and calcium silicate units. It is invariably greenish and occurs in 1-7 mm prismatic crystals, but has not been much studied.
Few assemblages have provided decent specimens or crystals. One such occurrence consists of blackish-green hedenbergite, calcite, pyrite, andradite, ferroaxinite, and fluorapophyllite from the Palmer Shaft at Franklin, and is described under fluorapophyllite (Betancourt, 1989). A second notable, but sparse occurrence is of superb greenish-brown, euhedral 2-5 mm crystals, in sprays associated with franklinite, rhodonite, willemite, and johannsenite, and discussed herein with the johannsenite which occurs epitactic on rhodonite from Franklin. An analysis of these latter crystals, showing minimal substitution of Mn and Zn and a composition approximating that of end-member epidote, with Al:Fe = 2:1. Specimens of epidote replacing scapolite are in some museum collections, but their source is ambiguous. Microcline is commonly associated.
At Sterling Hill, epidote was found as 4-5 mm crystals associated with stilbite and manganaxinite on the 1300 level, and it is locally associated with tennantite, actinolite, erythrite, and other minerals in various parts of the mine. An occurrence in a veinlet assemblage in wollastonite-bearing rocks was described by Jenkins (1994).
Epidote is very common in the mines at Balls Hill, especially the Gooseberry Mine, where it occurs in 10-cm masses associated with andradite, magnetite, and hedenbergite. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1801
     
 Formula: {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
 Essential Elements: Aluminum, Calcium, Hydrogen, Iron, Oxygen, Silicon
 All Elements in Formula: Aluminum, Calcium, Hydrogen, Iron, 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   Epidote

     
 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.404

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
View IssueV. 35, No. 1 - Spring 1994, pg. 21Geology and Mineralogy of a Veinlet Assemblage Associated With Wollastonite-Bearing Rocks, Sterling Mine, Ogdensburg, New Jersey, Robert E. Jenkins II - Epidote
View IssueV. 30, No. 1 - Spring 1989, pg. 8The Epidote-Pyroxene-Fluorapophyllite Assemblage in the Franklin Mine at Franklin, New Jersey, Philip P. Betancourt, Epidote (small description)
     
Images

     
Epidote crystals  from Sterling Hill. Actual image width 2 inches
Epidote crystals (green) from the Sterling Hill Mine, Ogdensburg, NJ. Image width 2" (51 mm). Photo by WP.


Epidote and salmon calcite from the Mill Site, Franklin, NJ. Photo by WP.
Epidote (green) and salmon calcite from the Mill Site dump, Franklin, NJ. 3 3/4" x 3 ". Photo by WP.







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