"I don't think it's plausible that there's any alloys that we can't identify," Richard Sachleben, a retired chemist and member of the American Chemical Society's panel of experts, told Live Science.... Alloys are mixtures of different kinds of elemental metals. They're very common — in fact, Sachleben said, they're more common on Earth than pure elemental metals are — and very well understood. Brass is an alloy. So is steel. Even most naturally occurring gold on Earth is an alloy made up of elemental gold mixed with other metals, like silver or copper. "There are databases of all known phases...