The force animating golems is magical in nature. The exact process that creates these hulking constructs is not fully understood, but according to multiple first-hand account witnesses, a cloud of purple-colored miasma coalesces around or into large piles of abandoned material being left in one place, which then animates and reshapes this material into the form of a golem, then continues animating it until it is destroyed. Goleme are hostile and seek to attack any living creatures they see, and there is absolutely no reasoning, taming, pacifying or capturing them - they will not stop attacking, ever, until destroyed. Upon destruction, what remains of the golem briefly shimmers purple as the miasma dissipates, suggesting that the miasma can no longer control something that has been sufficiently destroyed.
Gold golems are, as the name suggests, constructs formed out of gold, giving them the appearance of being animated golden statues. Their actual color varies from pale yellow to orange-ish, as the quality of the gold, depending on the quality of the actual gold they are made out of. It's not known exactly ''where'' they form, as refuse piles containing gold would sooner be looted than left alone long enough for the miasma to possess it. As such, they are considered to be rare and elusive.
Although no sightings of gold golems have ever been reported in bank vaults or active warehouses, their existence has motivated banks to start using unique, one-ingot, wooden protective cases, in order to "prevent" the creation of gold golems. There is no evidence that these ingot cases have ever prevented the creation of the golems, but it has entered bank vault management tradition ever since the first gold golems were sighted.