Phyllosilicate (sheet silicate), apophyllite group
Hardness: 4 to 5
Colour: Brownish-yellow, yellowish-brown, colourless
Solubility: Dissolved by hydrochloric acid with separation of silica (Dana, as natroapophyllite)
Common impurities: K
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. Please check the apophyllite page for more information.
Fluorapophyllite-(Na) occurs as a secondary mineral in amygdules or druses in basalt, in cavities in granite, in tactite and other metamorphic rocks, and as a late-stage hydrothermal mineral in some mineral deposits. Associated minerals include zeolites, datolite, pectolite, calcite and quartz (HOM).
At the type locality, the Sampo mine, Shitouyouze, Bicchu-cho, Takahashi City, Okayama Prefecture, Japan, fluorapophyllite-(Na) occurs in skarn as prismatic crystals alternately zoned with fluorapophyllite, and associated with zeophyllite, cuspidine and calcite (AM 66.416-423, Dana, as natroapophyllite).
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