Rare Mineral Found in Rock Elm Impact Crater450 to 475 million years ago, a meteorite slammed into w

Rare Mineral Found in Rock Elm Impact Crater450 to 475 million years ago, a meteorite slammed into west-central Wisconsin creating a 6.5-kilometer wide (4-mile) impact crater. Scientists have now discovered naturally-occurring reidite there, one of the rarest minerals on Earth. It’s only the 4th time it has ever been found.Reidite was first discovered in a laboratory in the 1960s. It’s a form of zircon (http://on.fb.me/1CgbhgZ) but 10% more dense. Zircon becomes reidite under extremely high pressure and temperature, such as the conditions created by impact shock waves, causing the molecules to pack together more tightly.Reidite was previously found at 3 other impact sites with the first being in 2001: the Chesapeake Bay Crater in Virginia, Ries Crater in Germany, and Xiuyan Crater in China. Those sites are composed of impact melt breccias – essentially a mix of unmelted angular rock fragments cemented together by crystals formed from melted rocks. The reidite found at Rock Elm is in sandstone - someplace scientists didn’t think it would be; in fact, they found it while collecting zircon to more precisely date the crater. The presence of reidite means the impact created a much higher pressure shock wave than previously thought; scientists had estimated it at 10 gigapascals (1 gigapascal = 1,000,000,000 pascals), but reidite needs 30 to 80 gigapascals of pressure to form.The discovery means that reidite might be more common than previously thought; sandstone impact sites typically have zircon, meaning that they might have reidite as well. Now that scientists know they should look for it, they will probably find it.- REImage Credit: Rock Elm Impact CraterBill Cordua (UW–River Falls) and the Wisconsin Geological and Natural History Surveyhttp://wisconsingeologicalsurvey.org/Image used with permissionRead More: http://wgnhs.uwex.edu/wisconsin-geology/meteorites/http://www.livescience.com/48584-reidite-discovered-rock-elm-wisconsin.htmlhttp://phys.org/news/2015-01-rare-mineral-wisconsin-crater.htmlhttp://www.astrobio.net/news-brief/rare-mineral-found-wisconsin-crater/#sthash.Mpp66Tjz.dpufhttp://www.psi.edu/epo/explorecraters/impactmeltbreccias.htm -- source link
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