This thread is for the posting of vintage collectible copper ingots, such as souvenirs from mines, smelters, etc. I have noticed that the market for vintage collectible copper ingots is quite strong recently, especially for those that are souvenirs from mining companies and refiners. I will start with this one. When I saw it offered for a fairly cheap price, I bought it for my collection of vintage non-precious ingots. Anybody who pours molten silver or copper knows that when it is very pure it will grow crystals as it cools into an ingot. This one really shows the crystals and I think that was the point of this promotional piece. As the light angle changes, different crystals "light up". This is probably the purest item of copper that I know of.
I don't have any copper bars or ingots Dan. Thats a cool ingot you have there. I will be on the look out.
Maybe unusual with the Cu element symbol. I purchased this neat Copper 1 Ounce at the Museum of Natural History gift shop in NYC. They have an amazing Rock, Minerals and Gem display there!
Getting big crystal grains like that requires fairly pure metal, but I think the more important factor is very slow cooling. Makes me want to try making some myself. (I did have to laugh at the bit about 99.99 being "the purest copper commercially obtainable" - especially coming from a company that claims to sell to the semiconductor industry, where 99.9999 sometimes isn't quite pure enough!) I'm remembering a tale from a materials-science friend, about a group that had ordered in a block of specially-annealed copper for some specialized use, at great expense. One of the lab workers dipped it in a solvent to remove any surface residue, then removed it and gave it a good shake to get rid of most of the liquid - and the block wrapped around his hand. And, of course, bending it work-hardened it, so it was ruined.
Better than 99.99% is certainly possible today. This AMAX round is from the 1970s, so there might not have been anything available with higher purity at the time.