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Test for rhodium? (found a 70 pound slab)

Q. I've found this 70+ lb silver slab of something. I was panning for gold when I came across it. It's 70+ lb and it's only 6 in x 8 in maybe 2 inches thick in some places, so it's got my curiosity flying all over the place. When I first brought it home I dusted it off and put the whole thing in Muriatic Acid [affil link] for a good 6 hours and in all due respect, this piece is not breaking down whatsoever.

After inspecting it I noticed right away a silvery shine to it. I filed some of the metal off of it and put it into muriatic acid--not much of a reaction and the mixture turned bright green. It's got me stumped but I'm sure it's something valuable because it won't break down (tough stuff). Is there a test I could perform at home to test for Rhodium? (Just hoping.)

Jostlyn McCarter
hobbyist - Salt Lake City, Utah
September 5, 2008

"Rapid Spot Testing of Metals & Alloys"
by Andrew Holmes
from Abe Books

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Hi, Jostlyn. It's very unlikely that someone misplaced a ten million dollar slab of rhodium :-)

Rhodium is so rare and dispersed that even at its astronomical price it has never been mined or refined for itself, only as a byproduct of platinum mining & refining. That slab is not rhodium.

You can see how much it weighs and how much water it displaces and thus determine its density (Archimedes Principle). That won't tell you exactly what it is, but will tell a lot of things that it's not; the heavier it is, the more things it isn't. You can see if your library can get you a copy of Rapid Spot Testing by A. Holmes. →
Can you find a jeweler who is equipped to quickly tell you what this slab is? Good luck.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

? Do you have a photo of this slab of metal ?

Leon gowen
- Little Rock Arkansas
December 28, 2022

A. Hi Leon
Good idea, and thanks for trying to help -- but Jostlyn's question is really old.
Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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