Janet Kaiser on wed 25 jul 01
Pyrites are crystals of metal sulphide minerals. It
depends if what you have are Iron Pyrites FeS2 or
Copper Pyrites CuFeS2 (a.k.a. Fool's Gold). I think
there are also cobalt and even tin pyrites, but have
never used them.
They may even appear in clay (especially fireclays as
glassy hard bits) although they are usually considered
to be "impurities" and extracted. Pyrites here in Wales
are seen as little sparkling specs in the slate and
quartz, rather than the lumps of Fool's Gold I have
seen in Hollywood movies...
They look like Marcasites which are crystalline iron
sulphide, and were used a lot in jewellery at one time.
They corrode and go rusty so the slate with pyrites is
considered inferior for most uses (roofing, floors,
worktops).
Pyrites produce attractive dark spots in reduced
glazes.
I think Chromite is a mix of Chromium and Iron oxides?
Janet Kaiser
The Chapel of Art . Capel Celfyddyd
HOME OF THE INTERNATIONAL POTTERS' PATH
Criccieth LL52 0EA, GB-Wales Tel: (01766) 523570
E-mail: postbox@the-coa.org.uk
WEBSITE: http://www.the-coa.org.uk
----- Original Message -----
> Two of the jars hold materials with which I am
> unfamiliar. One is Pyrites (I suspect this is an
iron of some sort - it
> is a blackish powder) and the other is granular
Chromite, shiny black
> grains a little larger than granular rutile. Does
anyone have any idea
> what these two chemicals might do?
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