Crystal System: Hexagonal Status of Occurrence: Confirmed
Occurrence - 1st UK recording Chemical Composition: Iron
manganese silicate hydroxide chloride Chemical Formula:
(Fe2+,Mn)8Si6O15(OH,Cl)10 Method(s) of Verification: Blaen-y-
Nant - optically and X-ray powder diffraction (Brown, 1959).
Introduction: pyrosmalite is a series with iron- and manganese-
rich end members - ferropyrosmalite and manganpyrosmalite
respectively. Pyrosmalite is often the name given to
undifferentiated members of this series, although has in the
past been used for iron-rich varieties. Pyrosmalite typically
occurs within metamorphosed rocks. Occurrence in Wales: this
rare mineral was described by Brown (1959), from the Nant
Ffrancon area in Gwynedd, where it occurs as small clusters of
radiating crystals in metasomatized Ordovician slates. Brown
suggested that given the preponderance of iron over manganese in
the host rock that,'it seems likely that the mineral is
pyrosmalite rather than manganpyrosmalite'. However, Brown also
notes