From this mineral you smelt copper.
Ancient people (and I'm talking about very ancient people, some 8000 years before christ) first started to use it to make beads or small pendants, using it for mere ornamental reasons, because of it's brilliant colours (the one you see here is a really raw one but it can also be found in an brighter green colour).
Who was the one that first put it in the fire? Who was the first to understand that putting it in high temperature you can turn it into copper? Who associated the product of this smelting from the element they already knew was disposable in nature (I mean the native copper ores)?
Those are really awesome questions, none of them could be answered. We only know that somewhere around 5500-4000 years before christ umanity started producing metals from their minerals and since then never stopped.