I'm not sure how to classify this topic but I have been looking at ways that using a metal detector to estimate a coin's conductivity may be useful to the collector (
https://www.forumancientcoins.com/board/index.php?topic=64089.0 ). Recently I bougt a Q.Titius
denarius which shows signs of "
crystallization" otherwise known as age embrittlement. Not a serious case but the conductivity is about 1/3 that of a sound
republican denarius - these being about 95+% pure silver which, of all metals, has the highest conductivity.
The method might be of use for determining whether a silver coin, especially one just found, needs special handling. Also since fakers can imitate the surface appearance of a crytallized coin , the method might be used to distinguish whether the coin is really old or artificially aged.
A "
crystallized" coin tends to fracture easily and the break looks crystalline (as in the close-up photo) since the micro-grains of silver fracture along their boundaries. They no longer stretch and give the metal its usual strength and ductility.
