Stony meteorites

Not always visibly stony

Some chondrites contain conspicuous iron-nickel metal, while basaltic achondrites can resemble terrestrial rocks. Appearance alone is therefore insufficient for classification.

Minerals and visible texture

Stony meteorites consist mainly of silicates such as olivine and pyroxene. Feldspar or its shock-altered form, sulphides and small amounts of iron-nickel metal may also occur. Despite the name, many therefore contain visible metal flecks.

Density, grain size and colour vary widely. An ordinary chondrite may show round chondrules, while an achondrite may resemble terrestrial basalt. Appearance alone does not reliably separate these families.

Two fundamentally different histories

Chondrites preserve largely unmelted starting material from the early Solar System. Their components accreted on small parent bodies and were later modified to varying degrees by heat, water, shock and pressure.

Achondrites came from bodies that at least partly melted and differentiated geologically. Magma, crystallisation, crust and mantle formation erased original chondrules. Stony meteorite therefore describes material, not one shared origin.