What do you call a silica-based life form that looks exactly like a human being? No, seriously. This isn't a joke; what do you call it? Well, if you're Verity Price, you call it "Marcy," and you let it take the difficult tables during the lunch shift.
The evolution of oreads is heavily debated among cryptozoological circles, as they really do seem to be silica-based, rather than carbon-based, although dissections are somewhat hampered by the need to use a rock hammer. Modern laser technology may help clear up some of the many, many linger questions, as soon as someone with the desire to dissect an oread learns how to use a laser, and gets hold of a dead oread (not easy).
Oreads appear all over the world, but are commonly named from the Greek, simply because those were the first ones most Western cryptozoologists encountered. They have human-level intelligence, and will generally self-identify as the common name for their race.
Some people regard oreads as a bit slow. They're not. They just don't see any reason to hurry things for you.