Samfowlerite



Samfowlerite is a zinc manganese beryllium calcium silicate hydroxide mineral. Microprobe and ion-microprobe analyses, with water by difference, yielded SiO2 36.9, MgO 0.2, CaO 34.1, ZnO 9.5, MnO 9.3, BeO 5.6, F 1.0, H2O 3.8, less 0=F 0.4, total = 100.0 wt. %.
Samfowlerite was first described from Franklin by Rouse et al. (1994). It has not been found at Sterling Hill.
The crystal structure of samfowlerite contains SiO4 and Si2O7 groups and is related to those of the epidote and pumpellyite groups and to that of vesuvianite. The structure is composed of layers of vertex-sharing TO4 tetrahedra (T = Si, Be, Zn) alternating with layers of vertex- and edge-sharing CaO, bicapped trigonal prisms and MnO6 octahedra. The TO4 groups and CaO8-MnO6 groups share vertices with one another across the layer boundaries to form the three-dimensional structure. Within the layers of tetrahedra, the TO4 groups form a network of 4-, 5-, and 8-membered rings.
Samfowlerite occurs as 0.5 mm euhedral vitreous colorless crystals; they may appear white in the aggregate. Only a few specimens have been found, and the crystals have not been studied goniometrically; recently found crystals are consistently twinned, but the twin law has not been determined. Cleavage is absent; the density is 3.28 g/cm3.
Some samfowlerite is fluorescent in both longwave and shortwave ultraviolet with an exceedingly weak red response color. Samfowlerite is visually similar to some nonfluorescent clinohedrite, but it has a much higher luster on the crystal faces. The apparently common but unstudied twinning may also aid in visual recognition.
Samfowlerite is known from but one rare assemblage from Franklin. Fortunately, however, it is a well-known assemblage for cahnite and was found in 1927, as reported by Palache (1935). The assemblage consists of franklinite-willemite-andradite ore which has vuggy areas. These vugs are lined with sparse 1-cm crystals of willemite and platy barite. Zoned garnet (andradite-grossular) has lined the vugs, grown contemporaneously with the willemite and barite crystals, and persisted in growth after their formation.
The zoned garnet is the most notable megascopic feature of the assemblage, varying in color and texture from yellow-brown granular material to an outer zone of whitish fine-grained zoned material forming dodecahedra with a thin pinkish outer skin. Of particular interest are very small, submillimeter-sized crystals of various minerals which occur as late-stage crystallites on this outermost zone of the garnet. These minerals are euhedral twinned cahnite crystals, pseudohexagonal clinochlore (called biotite by Palache, 1935), thin druses of very pale-pink leucophoenicite, and euhedral crystals of samfowlerite. Although based on the observation of very few specimens, samfowlerite tends to occur alone in vugs, or with clinochlore, and interstitial to platy crystals of barite. (Dunn, 1995)


 Location Found: Franklin (Type Locality), unique to Franklin/Ogdensburg area
     
 
 Year Discovered: 1991
     
 Formula: Ca28Mn6Zn4(Be,Zn)4Be12[(OH)3|(SiO4)3|(Si2O7)2]4
 Essential Elements: Beryllium, Calcium, Hydrogen, Manganese, Oxygen, Silicon, Zinc
 All Elements in Formula: Beryllium, Calcium, Hydrogen, Manganese, Oxygen, Silicon, Zinc
     
 IMA Status: Approved 1991
     
Fluorescent Mineral Properties

 Shortwave UV light: Weak red
 Mid wave UV light: Weak red
 Longwave UV light: Weak red
     
 To find out more about this mineral at minDat's website, follow this link   Samfowlerite

     
 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.419


The Picking Table References
 PT Issue and PageDescription / Comment
V. 58, No. 1 - Spring 2017, pg. 16Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Samfowlerite
View IssueV. 36, No. 2 - Fall 1995, pg. 11Technical Notes - Samfowlerite
     
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