It was originally classified as a eucrite, a group of meteorites thought to be from the asteroid Vesta.

BBC: Mercury meteorite puzzle

An Argentinian Pitt had never seen before showed up at his office door out of the blue, offering to sell Pitt a rare Eucrite meteorite weighing 3 pounds.

FORBES: They've Gotta Have It

For hard-core hobbyists, that's not a problem, and may even be a point of pride: It takes a practiced eye to distinguish between a eucrite and a diogenite.

FORBES: Hot Rocks