Ganophyllite



Ganophyllite is a potassium sodium calcium manganese aluminosilicate hydroxide hydrate mineral. Franklin material has been thoroughly analyzed. Unlike bannisterite, which has broad solid solution of Fe, Mg, and Zn for Mn, ganophyllite is principally a K-Mn-Al silicate with little substitution among the octahedral cations. The substitution of Al for Si is limited, and Mn is apparently limited to 7 of the 8 octahedral cations. The large cations are apparently ordered, and the water content, which is very loosely bonded, may vary, as in some zeolites and smectites. Dunn et al. (1983) suggested that ganophyllite might behave like a zeolite, and this was confirmed by Guggenheim and Eggleton (1986) and Komarneni and Guggenheim (1988).
Ganophyllite, first found at Pajsberg, Sweden, was described from Franklin by Palache (1910, 1935), Larsen and Shannon (1922, 1924), and Smith and Frondel (1968). The crystal structure was described by Jefferson (1978) and Kato (1980) using Swedish material. Ganophyllite was chemically reinvestigated by Dunn et al. (1983b). It is a layer silicate closely related to bannisterite and is known from Franklin, but not Sterling Hill. The most recent review is by Guggenheim and Eggleton (1988).
Ganophyllite occurs in two distinct crystal habits at Franklin. The first of these, described by Larsen and Shannon (1922), consists of prismatic crystals, which may form radial, cm-sized sprays, or be randomly distributed. The second habit consists of pseudohexagonal 1-2 mm platy crystals resembling some phlogopite. Ganophyllite is light brown, brittle, with perfect cleavage, a density of 2.77 g/cm3, and a vitreous luster. There is no discernible fluorescence in ultraviolet radiation. Ganophyllite is distinguished from similar species in part by its brittleness.
Most of the samples studied by [Dunn] were from two major assemblages, each representing one of the two crystal habits. The first and third assemblages reported by Palache (1935) were not observed by [Dunn]. Other occurrences are rare and represented by only a few specimens.
The assemblage described by Larsen and Shannon (1922b, 1924) consists of pink rhodonite crystals with marsturite rims, yellow manganaxinite crystals, elongate marsturite crystals and prismatic sprays of ganophyllite; atacamite is found rarely. This assemblage was further described by Dunn and Leavens (1986); the mineral called "bustamite" by Larsen and Shannon is now known to be marsturite. This material was acquired by major museums in the 1920's, but is not well represented in local collections.
The second assemblage is represented in local Franklin area collections, but is not well represented among the older holdings of the major museums. It might have been acquired in the 1950's when the Palmer Shaft pillar was removed and abundant amounts of lead silicates were recovered. Thus, this second assemblage might not have been known to earlier investigators. The bulk of the available ganophyllite specimens are from the area of a vein assemblage described by Baum in Hurlbut and Baum (1960) and from which charlesite (Dunn et al., 1983) was reported. Ganophyllite occurs as veins in ore; the examined specimens consist of both fresh and recrystallized material. Veins of fresh ganophyllite have hendricksite wall contacts and contain small amounts of rhodonite and willemite, the latter in very irregular segregations. Clinohedrite is present in small amounts and is in the center of the veins, crystallizing late in the sequence.
Altered and recrystallized specimens of this second assemblage show the same vein minerals and additionally show ganophyllite forming directly as rims on decomposed hendricksite. Pre-existing willemite is recrystallized and occurs as colorless to light-green prismatic crystals. In addition to these minerals, the altered assemblage is host to a large number of accessory minerals such as prehnite, thomsonite, roeblingite (Dunn, 1982a), charlesite, xonotlite, and many others. These likely formed under hydrated and mobilizing conditions; large cations (Pb,Ba,Ca,Na,K) are quite prominent, crystallizing late in this assemblage.
One other assemblage, consisting of ganophyllite in andradite and calcite, was observed; it might be a replacement of hendricksite. Others may be known. (Dunn, 1995)


 Location Found: Franklin
     
 
 Year Discovered: 1890
     
 Formula: (K,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2O
 Essential Elements: Hydrogen, Manganese, Oxygen, Potassium, Silicon
 All Elements in Formula: Aluminum, Calcium, Hydrogen, Manganese, Oxygen, Potassium, Silicon, Sodium
     
 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   Ganophyllite

     
 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.494

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.57


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 30, No. 1 - Spring 1989, pg. 16Research Reports, Ganophyllite
View IssueV. 25 No. 2 - Fall 1984, pg. 8Mineral Notes Research Reports, Ganophyllite
View IssueV. 16, No. 1 - February 1975, pg. 6Mineral Notes - Ganophyllite
View IssueV. 10, No. 1 - February 1969, pg. 6Mineral Notes - Bannisterite/Ganophyllite/Stilpnomelane
View IssueV. 8, No. 2 - August 1967, pg. 8Mineralogical Data - Bannisterite/Ganophyllite
     
Images

     
Ganophyllite crystals, hendricksite, roeblingite, clinohedrite and willemite from Franklin, NJ
Ganophyllite crystals (light to medium brown), hendricksite (black), roeblingite (porcelain white), clinohedrite (white) and willemite (light green) from Franklin, NJ. Field of view 1" x 3/4". From the collection of, and photo by Robert A. Boymistruk.


Ganophyllite crystals, franklinite, hancockite, hendricksite and willemite from Franklin, NJ
Ganophyllite crystals (light to medium brown), franklinite (black), hancockite (reddish brown), hendricksite (black) and willemite (light green) from Franklin, NJ. 4" x 2 1/2". From the collection of, and photo by Robert A. Boymistruk.







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