![]() |
|
Exsolution willemite is very
unusual at the Buckwheat... or it
was until
we dug up a few good-sized chunks of it, associated with calcite,
pyroxene, and
an unknown subtranslucent brown
mineral with an intense resinous
luster similar
to that of triplite (I say that because I'm looking at a piece of
triplite from
Argentina which could be the spittin' image). Everyone I've talked to says
this resinous mineral has to be tephroite for some
vague reason or
another, but I have this theory that it might be fayalite. This idea is near-blasphemy
to most Franklin collectors I've
talked to, but I plan to do some tests if I ever get around to
it. Recall that fayalite and tephroite form a series.
Tephroite and willemite form another series. Recall also that
fayalite was found in the Buckwheat tunnel that went from the Buckwheat
pit to the dump, and undoubtedly some of that rock found its way onto
the dump (see the Dunn monograph on the Franklin-Sterling Hill
minerals). Now, I ask you: why couldn't some of this
fayalite contain willemite? Here's another clue:
the willemite's fluorescence is not
nearly as bright as usual. It's sort of like the "black
willemite" from Sterling Hill which occurs with... guess
what...
fayalite. There is still much on the
mineral dumps that has escaped
study. This particular assemblage
was overlooked in all the studies I
know of, so I am not 100% confident when I'm told it must be
tephroite. At least I doubt that it's end-member
composition. I
just have a feeling it has some iron in it (easy enough to determine
with simple chemical tests). I've seen this material on the Trotter Dump as well as the Buckwheat. It is very interesting stuff. Light used: Superbright 2000SW. Film & camera settings: Shop-Rite 400 speed film; exposure time 2 seconds; f-stop 5.6; minor gamma reduction applied to scanned image. If time permits I'll take a better, larger photo of this specimen. |