Fluorapophyllite-(Na)

minerals

zeophyllite

cuspidine

pectolite

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Formula: NaCa4Si8O20F.8H2O
Phyllosilicate (sheet silicate), apophyllite group
Specific gravity:
Hardness: 4 to 5
Streak: White
Colour: Brownish-yellow, yellowish-brown, colourless
Solubility: Dissolved by hydrochloric acid with separation of silica (Dana, as natroapophyllite)
Common impurities: K
Environments

Igneous environments
Metamorphic environments
Hydrothermal environments

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).

Localities

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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