Goethite



Goethite is an iron oxide hydroxide mineral. One analysis of Franklin goethite (brown with black mammillary surface), performed by Lawson Bauer, yielded 2.48 wt. % Mn, 49.8 wt. % Fe, and 5.15 wt. % Zn.
Goethite was reported from the Buckwheat Dolomite by Palache (1935) and much of the material he called limonite is likely goethite. It is known from both Franklin and Sterling Hill.
Goethite is invariably brown; much local material is fibrous in habit, but some occurs as well-crystallized, bladed crystals in subparallel to divergent fasicles. Peters et al. (1983) illustrated many habits of goethite crystals from the Buckwheat Dolomite. The bulk of local goethite is massive; some specimens have botryoidal to mammillary surfaces; and much local material is ocherous. Fist-sized masses are known. No physical data have been obtained.
Goethite is not a major mineral locally. It is a mineral of weathering and alteration environments. It was found in the oxidized zone at the north end of the Franklin Mine, in the Buckwheat Dolomite, and as a matrix for secondary copper carbonates on the 200 level.
At Sterling Hill, goethite is common in the oxidized material from the surface pit workings, occurring as hollow nodules associated with hetaerolite, chalcophanite, and hemimorphite. The paucity of significant specimens may be due in part to the perceived unattractiveness of such specimens. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
 Year Discovered: 1806
     
 Formula: α-Fe3+O(OH)
 Essential Elements: Hydrogen, Iron, Oxygen
 All Elements in Formula: Hydrogen, Iron, 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   Goethite

     
 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.592

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.58


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 30, No. 1 - Spring 1989, pg. 9The Epidote-Pyroxene-Fluorapophyllite Assemblage in the Franklin Mine at Franklin, New Jersey, Philip P. Betancourt, Goethite (small description)
View IssueV. 27 No. 2 - Fall 1986, pg. 6Minerals of the Franklin Quarry, Philip P. Betancourt, Goethite
View IssueV. 24 No. 2 - Fall 1983, pg. 14Minerals of the Buckwheat Dolomite Franklin, New Jersey, Goethite (small description)
     
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