Rust bloom
Rust bloom is the patchy orange-brown rust that can break out on iron meteorites and metal-rich stones while they are being stored.
Many meteorite owners have noticed small spots of orange-brown rust suddenly appearing on a slice that once looked perfect. This outbreak is often called rust bloom. It happens when moisture from the air reacts with the iron-nickel metal, especially where chloride salts picked up from the ground are present. The rust can spread, flake and, in bad cases, crack the specimen.
Rust bloom matters because it can slowly ruin specimens and their scientific value. Some irons are known for being troublesome, including many pieces of Campo del Cielo from Argentina, while others stay bright for decades. Etched and polished slices are especially sensitive, because their metal surface is exposed.
To recognise it, look for orange, brown or sometimes greenish spots or droplets, often starting at cracks, edges or around inclusions. To prevent it, keep meteorites in a dry place, ideally in an airtight box with a desiccant such as silica gel, and handle polished surfaces as little as possible, because sweat from fingers contains salt. Never wash a meteorite in water. Some collectors treat rust with special methods, but these involve chemicals or tools and should only be done by adults with experience.
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Level: Explorer Ages 10 and up