Reidite is a rare mineral that has a hardness of 7.5.  It was recently discovered by researchers at a crater in Winsconsin.  The meteorite crater is about 450 million to 470 million years old making this reidite the oldest ever found.  No one would have guessed to find this mineral where they did.  Previously, reidite had only been found in rock that melted and cooled into glass but this discovery was found in sandstone.  Reidite is a dense form of zircon and it takes a lot of pressure to transform zircon into reidite.  This tells researchers that minerals at Rock Elm crater underwent an amount of pressure much higher than expected.

Click HERE to see the full article by Becky Oskin on Live Science.