Hematite



Hematite is a ferric-iron oxide mineral. Few analyses are known (Palache, 1935); local material is of near end-member composition, with but a few wt. % FeO and minor Mn. Bauer analyzed one specimen with Fe 54.5, Zn 8.9, Mn 7.0 % and another with 96.08 Fe2O3, 1.85 FeO, 0.22 Mn2O3, 1.02 MnO, 0.92 ZnO, total = 100.09 wt. %.
Hematite is found at both Franklin and Sterling Hill, but is not an economic ore mineral locally. The first report was of pseudocubic partings described and analyzed by Moses (1905); an occurrence of hematite was also noted by Ries and Bowen (1922).
Hematite is found as crystals and as mammillary, botryoidal, and ocherous, massive material. The best crystals from Franklin were described by Palache and Berman (1927) and Palache (1935). The forms are varied, and pseudocubic crystals with complexly formed coigns have been found here; twinning has been observed. The best known of local hematites are specimens bounded by parting planes, yielding highly lustrous pseudocubic fragments, varying from 11 cm (Frondel, 1935) to 17 cm (Frondel, 1972). The parting in such specimens is well-pronounced and appears similar to cleavage, which is absent. No intraparting minerals were noted by [Dunn], employing microprobe, reflected light, and X-ray studies.
Crystals of hematite are apparently black (very dark red), and fine-grained massive material is dark red. The luster of local material varies from splendent metallic to dull and ocherous. Hematite has been found exsolved in franklinite by Frondel and Klein (1965); they noted several types of exsolution. Carvalho (1978) and Valentino (1983) noted in a study of magnetite-franklinite exsolution intergrowths from Sterling Hill that some magnetite-rich lamellae have been replaced by hematite, and in some cases both magnetite and franklinite have been replaced. Valentino suggested that the former case could have been an example of what was studied by Frondel and Klein (1965).
Hematite is a minor mineral at Franklin and slightly more abundant at Sterling Hill. In addition to specific assemblages noted below, it also occurs sporadically as grossly and finely disseminated grains in many minerals, including calcite, willemite, and others. Ries and Bowen (1922) and numerous others have reported it replacing franklinite.
The best known specimens are the large parting fragments from Franklin; they have inclusions of franklinite low in Mn (Frondel, 1972) or magnetite and are associated with sparse andradite. Such material was found in the northern end of the Franklin Mine; one specific occurrence was on the 550 level at 760N. Fine crystals are known from the Buckwheat Dolomite (Peters et al., 1983), and many crystals have been found in seams and veins found sporadically in the ores. Superb, splendent, platy crystals, some forming rosettes up to 2 cm, are known from the 300 level, associated with lennilenapeite, magnesioriebeckite, sphalerite, and dolomite. Fine platy crystals up to several cm were also found with rhodonite, calcite, franklinite, and barite. Hematite is also associated with siderite.
At Sterling Hill, hematite is found sparingly in seams and veinlets, but is most abundant in the north orebody, where it occurs as dark-red ocherous to dense material, surrounding franklinite, and in convoluted and vein-like assemblages with serpentine, calcite, dolomite, and sphalerite.
The variety of hematite habits in the north orebody include botryoidal material, layers of specular platy material, and fine-grained blue-black-lustered masses. It occurred in thick masses at contacts with the Franklin Marble adjacent to the Zero fault; much shearing is common in these specimens. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 
     
 Formula: Fe2O3
 Essential Elements: Iron, Oxygen
 All Elements in Formula: 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   Hematite

     
 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.595

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.60


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 31, No. 1 - Spring 1990, pg. 3Breithauptite From The Nickel-Arsenide Assemblage at Franklin, New Jersey, Hematite (small description)
View IssueV. 27 No. 2 - Fall 1986, pg. 6Minerals of the Franklin Quarry, Philip P. Betancourt, Hematite
View IssueV. 24 No. 2 - Fall 1983, pg. 14Minerals of the Buckwheat Dolomite Franklin, New Jersey, Hematite (small description)
View IssueV. 7, No. 2 - August 1966, pg. 10The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Hematite
     
Images

     
Hematite showing parting planes from Franklin
Hematite showing parting planes (hematite does not have crystal cleavage) from Franklin, NJ. From the collection of, and photo by JVF.







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