catmanraon: That is the most verifiable definition for the time period I have heard.
One other that I recall, unsubstantiated at this time was allegedly per Gord's research when he wrote the song. I recall this vaguely from alt.music.lightfoot around '97 - '99 and when I've a little more time will look it up.
The word purportedly, from a member attending a concert and asking Gord if I recall (which of course does not make it correct) was from drunkards crawling under tavern floors on the ground, across uneven terrain where stones were used to support a (more) level foundation.
Supposedly the gold-seeker would pick up gold coins dropped through relatively wide cracks in the floorboards by drunkenness or fumbly-fingers (that'd be me LOL). No explanation given for the term's origin that I recall, other than the offerred definition from unknown reference material, but per the member that gave it, it was what Gord had found it to mean somewhere.
I find catmanron's better-substantiated definition more reliable now than my memory, but I hope it adds to the thread
geo Steve
ps my dentist calls the silver/alloy fillings "amalgam" so this term alone may be a more general term in metals. I friend of mine is a metallurgical engineer so I will ask if he has anything to add and report back, too.