Wednesday, June 29, 2011

Things You Find in the Field: Broken Fire Assay Crucible

When wandering out and about in the field sometime back in April, when the air still had quite a chill, and the snow had not completely gone, I came upon some bits and pieces of history: a few remains from fire assaying. This was a small site, not necessarily the location of an actual assay lab, maybe just a place where someone had dumped some miscellaneous debris.
Here's the biggest, most distinctive chunk I found: part of the bottom of a fire assay crucible, a crucible used in fire assay for gold and silver.
The inside has a thin coating of what was once fused ore and flux, now cooled to a greenish glass.
I think the bottom of the crucible holds a vague clue to the manufacturer of the crucible, and hence to its age, but not one I know how to decipher.

Fire assay / cupellation at Wikipedia - a fairly abbreviated description of the fire assay process.

What is Fire Assaying? - a more complete description.

A Textbook of fire assaying - by Edward Everett Bugbee, the classic and complete text on fire assaying. I used a 1933 edition of Bugbee when doing fire assays for my thesis.


Gaelyn said...

Too bad there wasn't any gold stuck in it. But fun finds.

Silver Fox said...

Ha! The whole point is to pour the gold out of the crucible into the cupel, then dissolve the lead away from the gold, and then weigh it. Hopefully, if there was any gold, the assayer kept the tiny little piece. :)