> Because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals. Consequently, economically exploitable ore deposits are sparse (i.e. "rare").
For the purposes of this conversation, which is about economics not geochemistry, they are in fact rare. At least the minerals are
ore deposits that aren't economically exploitable are uneconomic because the price in the market is too low to pay the necessary costs, which are higher when the concentration is lower
all this means is that there is a wide range of concentrations among ore deposits
it doesn't have anything to do with how high those prices are or how rare the minerals are, and as you pointed out upthread in https://news.ycombinator.com/item?id=34357834, the prices are pretty low
you said neodymium was US$400/kg; gold, the standard rare element, is US$60893/kg today
For the purposes of this conversation, which is about economics not geochemistry, they are in fact rare. At least the minerals are