Octahedrites are the most common structural class of iron meteorites. The structures occur because the meteoric iron has a certain nickel concentration that leads to the exsolution (when a solid solution becomes unstable) of kamacite out of taenite while cooling. Due to a long cooling time in the interior of the parent asteroids, these alloys crystallize into intermixed millimeter-sized bands (from about 0.2 mm to 5 cm). When polished and acid-etched, the classic Widmanstätten patterns of intersecting lines of lamellar kamacite, are visible. In gaps between the kamacite and taenite lamellae, a fine-grained mixture called plessite is often found. Graphite and troilite occur in rounded nodules up to several centimeters in size. Offered here is a 3.75x4x2.25" tall coarse iron octahedrite meteorite w/Type IA silicate inclusions that weighs 3 lbs. This meteorite fell in the Campo del Cielo region on the border between the provinces of Chaco and Santiago del Estero, 620 miles northwest of Buenos Aires, Argentina. It is estimated that this meteorite fell 4,000 to 5,000 years ago, and was first discovered in 1576. The craters and the area around contain numerous fragments of iron meteorite. The total weight of the pieces recovered so far exceeds 100 tons, making the meteorite the heaviest ever recovered on Earth. The largest fragment, consisting of 37 tons, is the second heaviest single-piece meteorite recovered on Earth, after the Hoba meteorite. This is a complete "natural" specimen, showing flow lines and its original weathered surface, which has scattered oxidation given the high iron content of this meteorite. Makes for an out-of-this-world display. From the Robert M. Overstreet Collection and comes with COA.