Most people know perfectly well that
rocks minerals can look incredible on the inside – but this cross-sectional view of a meteorite still caught us by surprise.
The space rock pictured above is a chunk of the Alvord Meteorite, discovered in Iowa in 1976. The criss-crossing, internal structure seen here is known as the Widmanstätten Pattern. Commonly found in iron meteorites, the distinctive design is formed as the liquid metal at the core of a newly formed meteorite (comprising mostly nickel and iron) cools very slowly over the course of millions of years. (One estimate puts the cooling rate of these molten-core meteorites at 1°C every thousand years.) The result is a lattice of nickel-iron crystals unlike anything seen here on Earth. (For a more detailed account of this cooling process, see here.)
More info, via the Iowa DNR Geological Survey Bureau:
ALVORD METEORITE: The Alvord Meteorite was found on or around June 5, 1976, on a farm about 13 miles southeast of the Lyon County town of Alvord. Arnis History of Meteorites lists it as weighing 17.5 kg (38.5 lbs) when found and being an iron octahedrite (IVA). The find location was listed as 43º 19’ 20” N, 96º 17’ 20” W. New information indicates that the meteorite was found by Herbert Van Engen on the John Mulhall farm, T98N, R46W, Sec 09, north half, about a mile southeast of Alvord. The meteorite was eventually sold to the National Museum of Natural History, Smithsonian Institution for $800, however a slab was cut and retained by the Van Engen family as a souvenir.
A second piece was found in 1981 during Fall plowing by Jim Kelly. This fragment weighed 39 pounds and was found in T98N, R46W, Sec 03, southwest quarter, about 1.5 miles southeast of Alvord. This sample was sold to the Smithsonian Institution for $800.
Jim Kelly also reported that a curve on the “outside” of the meteorite suggested that the original body was about the size of a “medicine ball” (about 18” in diameter) and he believes that it fell in the 19 teens when his father observed an explosion in the sky that was attributed at the time to an exploding meteorite.