Touchstone Use On Ancient Gold Coins?

[Kevin D]

Has anyone seen what they thought might be a touchstone mark on the edge of an ancient gold coin? (I realize that a touchstone mark might be hard to discern from a randomly occurring mark). If yes, can you describe the coin and mark?

Any info on literature that discusses this, or mentions use of a touchstone on coins in ancient times, will be appreciated.

[JBF]

Plato refers to a touchstone, I forget the context but for the best people they have a soul of gold, so to speak.  So he might use it as an analogy, or perhaps for gold a touchstone works, but for a golden soul, there is nothing comparable??  Get a collection of Plato's dialogues, (and one of Aristotle too, while you are at it, (from Library), and look it up in the index.  I would look it up in mine, but I am not going to be home for awhile.  There may be in other philosophers the use of the same analogy, I don't know.  Maybe also, Church Fathers.

[Dino]

JBF, I think Kevin is talking about a different type of touchstone.  One used to test gold content.

"A touchstone is a small tablet of dark stone such as fieldstone, slate, or lydite, used for assaying precious metal alloys. It has a finely grained surface on which soft metals leave a visible trace."


Kevin, I have not.

[Kevin D]

Thanks to both of you for your input.

I believe I've read that the use of acid with the touchstone is a 'newer' development, and that originally it was simply a color comparison with other samples of known purity.

I found this and feel it is well worth passing along:
Assaying in Antiquity by Andrew Oddy
https://core.ac.uk/download/pdf/81204356.pdf

[JBF]

Actually Plato refers to "the gold (the metal) detecting" touchstone, I think (but could be wrong) that he might be talking about it metaphorically, but not _just_ metaphorically.  'Wouldn't it be great if we had something that could detect gold souls, just like we have a touchstone that detects gold.'  Something like that.  I don't remember, but there is at least one reference to "the gold (metal) detecting" touchstone.  a gold touchstone is a popular metaphor for ancient philosophers.

Whether a cultural use of the item in an ancient dialogue is what you're looking for is another question.  I would also look at Pliny the Elder in his Natural History.