In addition to what other posters have said, chemotrophic bacteria can play a significant role concentrating/enriching certain metallic ores by eating dissolved minerals in deep groundwater and metabolizing out metals. Lots of vein-gold runs through very old & fractured marble/granite bedrock with a lot of hydrologic activity.
Remove downvotes. Unironically, its a good idea. Requires people to actually engage with something if they disagree rather than just downvote and move on. Gets people talking & raises user engagement. Will be an uptick in shitflinging for a short while till all the assholes out themselves, get banned, and site culture improves from that alone.