Dan Demeo writes:
"With regard to Rafael Delgado's inquiry
about metals having specific gravity around 7 (6.9-7.3), there
are lots of choices, some of which could be eliminated easily:
- chromium--7.20, but too hard to strike coins
- cast iron--7.2--but brittle, and it rusts
- tin--7.28--a good possibility
- zinc--7.14--another good one
There are quite a number of metals and alloys which fit the
range specified. One way to determine the composition is to
put the object in a scanning electron microscope (SEM) and
analyze the surface using energy dispersive x-ray analysis
(EDX). PCGS has had this done, so Mr. Delgado should
be able to have his object (coin?) analyzed or authenticated
through them. Or, he could look up local laboratories offering
SEM/EDX services or x-ray fluorescence services. On the
bad side, it might cost several hundred dollars for the analysis,
but he will have an answer, which is always better than all the
guesses in the world."
Wayne Homren, Editor
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