What does a weathered meteorite look like?
A weathered meteorite is brown or rusty, with patchy or missing crust, rust stains inside and sometimes cracks, and it may look like an ordinary brown rock.
Many meteorites found on Earth have spent years, centuries or thousands of years on the ground, and they look quite different from fresh falls.
Outside. - The black fusion crust turns brown or reddish-brown as iron oxidises. - Crust may be patchy or completely lost, especially in deserts where windblown sand polishes stones. - Rust may stain the surface and nearby soil. - In hot deserts, stones may have a shiny dark coating of desert varnish, or a pale coating of calcium carbonate on their undersides. - Cracks may appear, filled with rust or minerals from the soil.
Inside. - When cut, the interior may be brown or orange rather than grey, because rust has spread through it. - Metal flecks may be dull or replaced by rust, with rusty halos around them. - Chondrules may still be visible, which helps identification.
Iron meteorites. - Weathered irons are covered in a rusty crust, sometimes thick and layered. - They may look like scrap metal or iron ore. - Some have shale, a layered rust crust that flakes off.
Weathering grades. Scientists describe weathering on a scale from W0, fresh, to W6, heavily altered.
Identification. Weathered meteorites can be harder to recognise. They may still be heavy and magnetic, but less so than fresh ones as metal turns to rust. Laboratory analysis may be needed.
Storing weathered meteorites dry is important to prevent further deterioration, especially for irons, which can continue to rust and crack.