IRON, FINE OCTAHEDRITE KIRUNA, SWEDEN (67°48’ N, 23°6’ E)

A MUONIONALUSTA METEORITE CUBE — CRYSTALLINE STRUCTURE OF AN IRON METEORITE DRAMATIZED IN THREE DIMENSIONS

Located near the Muonio River in northern Sweden above the Arctic Circle are Muonionalusta meteorites. While meteorite hunters unearthed numerous masses in recent years, it was back in 1906 that children discovered the first Muonionalusta while engaging in a favorite childhood pastime: kicking what was an unexpectedly dense object—which in this instance was later verified to be a meteorite. Possessing what is among the highest terrestrial ages of any meteorite, Muonionalusta fell to Earth about one million years ago when the region was glaciated—and it has experienced four different ice ages since then. Muonionalusta specimens are believed to be glacial erratics (material transported by a glacier), and their exposure to churning rocks and ice for a million years would account for the smooth surface and nondescript shapes of most specimens. Despite its age, many specimens exhibit only minor interior weathering due both to the stability of the material as well as the specimen’s preservation in the deep freeze of the Arctic. For Mounionalustas, it’s is all about the splendor within; when sliced and etched and fashioned into slices, spheres and cubes, Muonionalusta showcases its internal crystalline resplendence. Also known as a Widmanstätten pattern, this intergrowth of two iron-nickel minerals that forms an unearthly metallic grid in shimmering shades of gray and silver; it is completely diagnostic of an iron meteorite. Muonionalusta is also the first iron meteorite in which stishovite was discovered, a rare and extremely hard silicon dioxide polymorph of quartz formed by tremendous shock pressure (in which the hypervelocity of an asteroid impact in the depths of interplanetary space is required).