About 94 percent of all meteorites found are stony meteorites. These are much harder to identify than iron meteorites because they are difficult to distinguish from ordinary earth rocks. Most are composed of rocky materials, mostly silicates, and are similar to the rocks of the Earth's mantle. There are three varieties: chondrites with small roundish mineral inclusions called chondrules; carbonaceous chondrites with chondrules of carbon compounds; and achondrites without chondrules and resembling earthly basaltic rocks. The particular example below, while it serves to visually represent the stony meteorites, is among the rarest of the rare. It is an achondrite, and because of its specific chemical composition, it is thought to have been formed on Mars. Presumably it was launched into space perhaps in an asteroid collision and travels millions of years before colliding with the Earth in the Antarctic. (More below the image.)

Many meteorites, including this one from Mars, have a thin black or reddish crust on their surfaces. This crust is easily visible in this image, particularly along the top and left sides. The crust is formed at high temperatures as the object plummets through the atmosphere. Most other characteristics of stony meteorites require lab analysis. Image courtesy of NASA.

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