Muonionalusta Siderite Sample
April 06, 2022
Photographer: Thierry Lombry
Summary Author: Thierry Lombry
This photo showcases a specimen of Muonionalusta siderite found in Sweden in 1906, of which 500 pounds (230 kilograms) were collected. The sample above weighs 338 grams and measures 3.2 x 2.6 x 1.1 inches or 8.13 x 6.6 x 2.8 centimeters, making its density 7.5 g/cm3. Siderites are iron meteorites and this sample fell approximately 1 million years ago. Originating 4.56 billion years ago, this family is one of the oldest meteorites.
This specific specimen contains more than 91% iron - which explains the difficulty in cutting and polishing it - 8.4% nickel and traces of rare elements (0.33 ppm of gallium, 0.133 ppm of germanium and 1.6 ppm of iridium) . It is an example of a fine octahedrite (Of), the most widespread of the siderites, of group IV A. Being a metamorphic meteorite, it formed in the heart of an asteroid of 31 to 68 miles (50 to 110 km) in radius that exploded following a collision. Crystallization occurs after the metal has melted. Cut, polished and acid etched, this siderite sample features the Widmanstätten pattern that formed in temperatures between 1000 and 700 Kelvin. To preserve its quality, this specimen has been treated and protected against corrosion since rust would appear within 6 months if left exposed.