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Re: Taconite

On Sat, 11 Dec 1999, Michael Grace wrote:
> I recently collected some rocks from northern Minnesota that are much like
> slate in form, but are darker (black) in color.  Multifaceted, very angular.
> IMO they would provide a nice contrast in a plant tank.  Based on the
> region, I guessed they were Taconite, but emailed the Minnesota Geological
> Survey group to get an expert opinion.  The response is below.  I would
> appreciate any knowledge or opinions on the suitability of Taconite in an
> aquarium.  Thanks in advance.

Pyrite (fool's gold) in the rock may be a problem, but it's not likely to
be a major problem unless there's enough there for you to actually see the

The rocks we use in aquariums should be well-weathered.  This isn't
fool-proof but it provides some assurance that the rocks will not contain
reactive minerals like pyrite or soluble minerals like gypsum.  I prefer
stream-rounded stones and advise against the use of any mined or quarried
rock.  The angularity of your rocks obviously means that you don't have
stream-rounded stone.  If you took the rocks from a natural outcrop and
not from a road cut, mine face or dump it's probably still weathered
enough to be safe.  If you did take it from one of those artificial
exposures, or some similar sort of excavation, then you may not want to
use it.

Roger Miller