OXIDESome may have noticed i said - copper oxides formed = various kinds of copper.
Yes.. i said and meant - oxide.
The copper oxidizes and only after it's picked up by a sulphide it's labelled - sulphide.
Perhaps too technical but.. after researching oxides turning to sulphides, i just couldn't accept
the entirety of, sulphides.
If an iron or copper, or any other metal oxidizes - surely, there's some oxides that don't bondwith a salt, and remains in oxide form.
Hence... test for both oxide and sulphide copper.
Cheers....