I heard from a video that the Spanish when they conquered major parts of the Americas considered platinum little more than a troublesome imitation silver and once dumped tonnes of it into the Atlantic, possibly to avoid its circulation as a counterfeit silver. The term "Rejected silver" itself is used in Jeremiah in a metaphor describing silver that refuses to be purified in the furnace. I wonder if this "Rejected Silver" is actually a reference to a metallic element that was mistaken for silver with attempts to get silver from it obviously failing, it received the moniker of "Rejected Silver" and if this hypothetical Silver like element is Platinum or another possible candidate metal
No, in verse 29 it says:
“The fiery bellows of judgment burn fiercely. But there is too much dross to be removed. The process of refining them has proved useless. The wicked have not been purged.” Jeremiah 6:29
It’s dross, it is a metal substitute that is worthless to give the coin the same appearance, but is worthless. In this period it was probably lead.
It’s like the 1964 quarter was 90% silver and if you find it keep it (1964 or earlier), because the metal is worth way more than a quarter, but any quarter after 1964 isn’t worth anything when melted.
If the dollar failed, the modern quarter would have no value. It would be almost impossible to use for exchange, but if the dollar failed and you had a 1964 quarter, the metal content would be valuable enough to exchange.
Literally, God is saying that they have so much lead (dross) in them that it isn’t even worth trying to get the little bit of silver that is in the coins. It is a metaphor for their souls.