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Formula: K7(Mg,Mn2+,Fe2+,Zn)48(Si,Al)72(O,OH)216.16H2O
Phyllosilicate (sheet silicate), stilpnomelane group
Crystal System: Triclinic
Specific gravity: 2.72 measured
Hardness: 3
Streak: Brown
Colour: Very dark in hand sample, chips are dark brown or light green
Common impurities: Ca,Ba,Na
Environments
Metamorphic environments
Hydrothermal environments
Localities
At the type locality, the Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA,
lennilenapeite is found in two different assemblages; it is both a
primary and a late stage
secondary mineral in the metamorphosed
zinc deposit.
The first assemblage contains nelenite,
clino-suenoite,
franklinite and
willemite as coarse grained aggregates having a
pegmatitic texture. The lennilenapeite occurs as
5 mm clusters of bladed crystals within clino-suenoite,
willemite and nelenite, but is
concentrated at the contacts between those species.
In the second assemblage lennilenapeite occurs as light green to light brownish green druses of platy crystals
on sphalerite and dolomite.
This is a low temperature hydrothermal assemblage
(CM 22.259-263, 35.219-246).
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