I'm addressing this particularly to James and all you Michigan-types.

We are in the process of cataloging some artifacts from around the base
of the "New Furnace" (ca. 1854) at the McIntyre Iron Works in Tahawus,
N.Y., and have found numerous pieces of large (5-10cm) flakes of iron
containing a fair amount of silicate. They are fairly thick (up to a
centimeter) and have a layered texture. They look most of all like the
rust flakes that have fallen off an old cauldron I have in my back yard,
except that they have no formed surface.  They were located on or near
the casting floor. What are they? Are they some sort of slag? I can
provide photos off list, if you wish.

Marty Pickands
New York State Museum