Fluorapophyllite is a potassium calcium silicate fluorine hydrate mineral. Partial microprobe analysis of crystals yields: SiO2 50.9, CaO 24.6, K2O 4.2, Na2O 0.4, F 1.9, less O=F 0.8 wt. %, indicating that this material is near the fluorine end-member in the fluorapophyllite-hydroxyapophyllite series.
Fluorapophyllite occurs at Franklin and was first described (as apophyllite) by Palache (1935). Frondel (1972) reported a Sterling Hill occurrence of apophyllite, undifferentiated as to species; this material has not been examined.
Fluorapophyllite occurs as euhedral, highly lustrous crystals, up to 15 mm in size, tabular, and as clusters of such crystals slightly offset from one another. It is white to pink to off-white and has a perfect cleavage, which exhibits a pearly luster; it has a vitreous luster on crystal faces and fracture surfaces. No physical or optical measurements have been made. The material resembles common fluorapophyllite in every way. There may be no discernible fluorescence in ultraviolet.
Franklin fluorapophyllite was described by Palache (1935) as occurring in the gneissic footwall of the Palmer Shaft at 600 feet on the incline. Bauer's catalogue indicates the specimens were found in 1907. Much of this material has been preserved, and it is found in many local collections. The matrix for most specimens is hedenbergite and epidote, associated with pyrite, ferroaxinite, zircon, natrolite, calcite, and other minerals. The assemblage is described in detail by Betancourt (1989).
Other occurrences may exist, but have not been studied. Lovely 6 mm clusters of light pink crystals, undifferentiated as to species, are labeled in the Harvard collection as being from the 910 pillar, 900 level, 35 feet from the footwall and near the Palmer Shaft. Fine 1-2 mm light pink crystals were found in 1990 on the 340 level at Sterling Hill; they have not been analyzed for fluorine or water. (Dunn, 1995)

 Location Found: Franklin and Ogdensburg
 Mineral Note: Known as fluorapophyllite in earlier mineral lists.
 Formula: KCa4(Si8O20)(F,OH) · 8H2O
 Essential Elements: Calcium, Fluorine, Hydrogen, Oxygen, Potassium, Silicon
 All Elements in Formula: Calcium, Fluorine, Hydrogen, Oxygen, Potassium, Silicon
 IMA Status: Approved 1976
Fluorescent Mineral Properties

 Shortwave UV light: Weak white
 Additional Information: Phosphoresces weak white
 To find out more about this mineral at minDat's website, follow this link   Fluorapophyllite-(K)

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.492. 'Fluorapophyllite'

The Picking Table References
 PT Issue and PageDescription / Comment
V. 57, No. 2 - Fall 2016, pg. 18Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Fluorapophyllite-(K)
View IssueV. 34, No. 2 - Fall 1993, pg. 13Recent Mineral Finds From The Sterling Mine Ogdensburg, New Jersey - Fluorapophyllite
View IssueV. 33, No. 2 - Fall 1992, pg. 10The Check List of Franklin-Sterling Hill Fluorescent Minerals - Fluorapophyllite (Fluorescent Info)
View IssueV. 30, No. 1 - Spring 1989, pg. 8The Epidote-Pyroxene-Fluorapophyllite Assemblage in the Franklin Mine at Franklin, New Jersey, Philip P. Betancourt, Fluorapophyllite (small description)
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