Bostwickite



Bostwickite is a calcium manganese silicate hydrate mineral. The chemical analysis yielded MgO 0.9, CaO 5.1, Mn2O3 56.3, Fe2O3 0.5, A12O3 1.0, As2O5 1.0, SiO2 20.1, H2O (by difference) 15.1, total = 100.0 wt. percent.
Bostwickite was known to mineralogists for over a century, but was undescribed, in part due to the soft and friable nature of the aggregates and the paucity of clean material. It was considered to be arseniosiderite by Palache (1935) and was shown to be a manganese silicate by Frondel (1972) and Dunn (1979c). It was described and named bostwickite by Dunn and Leavens (1983). It is known only from Franklin. The unit-cell and crystal structure are unknown.
Bostwickite occurs as hemispherules and radial aggregates up to 3 mm in diameter. It is brownish-red; weathered surfaces are darker brownish-red. It has vitreous luster and is very soft. The crystals are bladed, composite units, made up of many crystallites. The density is 2.93 g/cm3 or greater.
There is no discernible fluorescence in ultraviolet. Bostwickite is best distinguished using its unique X-ray diffraction data.
Bostwickite is known from but one occurrence from which a number of specimens were saved; most of these are in the collection at Harvard University. It was found in the Taylor Mine (later part of the Franklin Mine) in 1874. Bostwickite occurs as flattened hemispherules on medium-grade ore consisting of franklinite, calcite, and fluorite, with minor willemite. Bostwickite occurs directly on the ore surface and on secondary carbonates which coat the ore in part. The "back" side of the sample contains the type material for kittatinnyite, an even rarer mineral. (Dunn, 1995)


 Location Found: Franklin (Type Locality), unique to Franklin/Ogdensburg area
     
 
 Year Discovered: 1983
     
 Formula: CaMn6Si3O16 · 7H2O
 Essential Elements: Calcium, Hydrogen, Manganese, Oxygen, Silicon
 All Elements in Formula: Calcium, Hydrogen, Manganese, Oxygen, Silicon
     
 IMA Status: Approved 1983
     
     
 To find out more about this mineral at minDat's website, follow this link   Bostwickite

     
 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.515


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 25 No. 1 - Spring 1984, pg. 5Mineral Notes Research Reports, Bostwickite
View IssueV. 24, No. 1 - Spring 1983, pg. 12Mineral Notes A Mineral New To Science, Bostwickite
     
Images

     
Bostwickite, calcite, fluorite, franklinite and minor willemite from Franklin, NJ.
Bostwickite (reddish brown spray), calcite (white), fluorite (beige), franklinite (black) and minor willemite from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.


Bostwickite, calcite, fluorite, franklinite and willemite from Franklin, NJ
Bostwickite (brown spray), calcite (white), fluorite (beige), franklinite (black) and willemite from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.







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