True, though understanding the mechanisms of ore formation is a substantial advance. There's a critical distinction between the abundance of chemical elements

True, though understanding the mechanisms of ore formation is a substantial advance. There's a critical distinction between the abundance of chemical elements within Earth's crust and how, where, and when they are concentrated. I'm not generally familiar with the topic, but of a few instances: - Most iron ore is of biological origin, with so-called "banded iron formations" (BIFs) being largely formed in two episodes, ~3 billion and 1 billion years ago, largely by early bacteria. - "Rare earths" aren't so much rare as unconcentrated. By overall abundance, these are fairly common, but because they do not form ores, they're found at low concentrations, and are often recovered as by-products of other mining activities. Keep in mind that the issue of ore formation and its reliance on processes specific to Earth's geological evolution, including plate tectonics and biological activity, mean that prospects for mining on other worlds (the Moon, Mars, asteroids) are likely to face radically different circumstances. Then again, mining in such areas would also likely be focused strongly on substances considered generally abundant on Earth, such as oxygen and water.