Campo del Cielo iron meteorite. Structural classification is coarse octahedrite. The slice displays the classic Widmanstatten pattern (a.k.a. Thomson structure) found in some iron-nickel meteorites. This pattern results from the interweaving of crystals from two iron alloys, kamacite (low nickel) and taenite (high nickel). The Widmanstatten pattern is diagnostic of meteorites as this pattern cannot be duplicated in laboratories on Earth. To expose this pattern I first sliced the meteorite in half. Using various grades of emery cloth I polished the face of the sliced piece to a mirror finish. After polishing, the surface was etched with a 1:2 ratio mixture of 10% hydrochloric acid and 3% hydrogen peroxide. This creates a strong oxidizer in the presence of an acid, which is able to slowly eat away the iron. The varing rates of corrosion between the different iron alloys (kamacite and taenite) creates the Widmanstatten pattern of inter-locking iron crystals. The lower photo shows the intact meteorite. The middle photo shows the polished slice. The top photo shows the iron crystals that appear after etching.