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Formula: KCa4Si8O20F.8H2O
Phyllosilicate (sheet silicate), apophyllite group, forms a series with
hydroxyapophyllite-(K)
Crystal System: Tetragonal
Specific gravity: 2.33 to 2.37
Hardness: 4½ to 5
Streak: White
Colour: Colourless, pale green, aquamarine, white, pink, yellow
Common impurities: Al,Na
Environments
Igneous environments
Metamorphic environments
Hydrothermal environments
Basaltic cavities
Historically all the apophyllite group minerals were reported simply as
"apophyllite", and indeed it requires analysis to
differentiate between them, so there is comparatively little information about the individual members of the group, except in
recent times. See the apophyllite page for more information.
Fluorapophyllite-(K) is a secondary mineral in cavities in
basalt, cavities in granite, in
tactites and in some hydrothermal veins
(Mindat).
Localities
At the Basalt Quarry, Ambariomiambana, Ambohimalaza Commune, Sambava District, Sava, Madagascar,
fluorapophyllite-(K) crystals to 3 cm have been found in small cavities in the main quarry wall
(Min Rec 41-3.242).
At the Wiwatersrand goldfield, South Africa, fluorapophyllite-(K) is found rarely, and always with
quartz, which it postdates. Specimens have been recovered from the Stilfontein
and Mponeng mines, coloured colourless through white to pale green, the last caused by
secondary mineral inclusions
(R&M 96.4.324-325).
At the Dara-i-Pioz Glacier, Districts of Republican Subordination, Tajikistan, Fluorapophyllite-(K) is an associate
of fluorapophyllite-(Cs)
(CM 57.965–971).
The Central Mine, Central, Keweenaw county, Michigan, USA, initially targeted a series of sub-parallel mineralised
fissure veins where the most copper-rich portion of the vein was close to the
base of the main greenstone flow.
Although not particularly common, some fine apophyllite-(K) specimens from the Central mine do exist
(MinRec 54.1.53-81).
The Cliff Mine, Phoenix, Keweenaw county, Michigan, USA, is situated at the base of a roughly 70-metre
basalt cliff. A curious feature of the impressive thickness of the
greenstone flow here is that it contains zones of “pegmatoid”: areas
where
slow cooling in the core of the lava flow allowed for large feldspar crystals
exceeding 1 cm to grow. Such features are normally only observed in intrusive igneous rocks and are almost unheard of
in basalt flows.
The Cliff mine primarily exploited rich copper mineralisation in the Cliff
fissure (vein). Although mineralised with copper to some extent along its
entire length, the part of the vein just below the greenstone flow
carried the richest copper mineralisation by far. A significant amount of the
copper recovered at the Cliff mine came from amygdaloids in the tops of 13
basalt flows which were cut by the Cliff vein. The discovery and mining
of this vein proved that the veins were the source of the large masses of float
copper that were already well known, and proved that the
primary ore mineral in the district was native
copper, not sulphides, as had been suspected earlier.
Fluorapophyllite is much less common at the Cliff mine than at other fissure mines in the area. It occurs as
small, colourless and transparent crystals to about 1 cm, mostly in the vein itself
(MinRec 54.1.25-49).
At Fanwood Quarry, Watchung, Somerset county, New Jersey, USA, only a handful of specimens of fluorapophyllite-(K)
are known to exist. Glassy crystals up to 1 cm on datolite have been collected
in the middle amygdaloid
(Minrec 41-2.166).
At the Braen Quarry, Haledon, Passaic county, New Jersey, USA, fluorapophyllite-(K) is relatively uncommon and
occurs as isolated crystals on datolite,
prehnite or calcite or directly
attached to the walls of breccia cavities
(Min Rec 40-6.516).
At Wind Mountain, Cornudas Mountains, Otero county, New Mexico, USA, fluorapophyllite-(K) is an associate of
windmountainite
(CM 58.477-509).
At New York City, New York, USA, lustrous white fluorapophyllite-(K) crystals are found filling seams in
schist and gneiss. Beneath
Roosevelt Island, plates to 21 cm across of colourless, transparent to translucent fluorapophyllite-(K) crystals
to 12 mm have been. Tabular, translucent, greenish fluorapophyllite-(K) crystals to 18 mm across have been
recovered from the tunnel in areas under Queens and Manhattan
(R&M 84.3.226).
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