What are meteorites made of?
Meteorites are made of the same chemical elements as Earth, mostly as silicate minerals such as olivine and pyroxene, iron-nickel metal and iron sulfide. Some also contain clay minerals, water and carbon compounds.
There is nothing in a meteorite that is unknown on the periodic table; the elements are the same ones found on Earth. What makes meteorites special is the way those elements are combined, and the fact that many preserve materials from the very birth of the Solar System. Stony meteorites are built mainly from silicate minerals, compounds of silicon and oxygen with metals such as magnesium, iron and calcium. The commonest are olivine, a greenish mineral also found in Earth's mantle, and pyroxene, often accompanied by plagioclase feldspar. Many stony meteorites also contain flecks of iron-nickel metal and a bronze-coloured iron sulfide called troilite, which you can sometimes see sparkling on a cut face.
Iron meteorites are made largely of iron alloyed with nickel, typically several per cent nickel and sometimes much more. The metal occurs as two alloys, kamacite and taenite, which form the striking crystal pattern revealed when an iron is cut, polished and etched. Stony-irons, such as the pallasites, combine metal with silicate crystals in roughly equal amounts.
Some rarer types have very different recipes. Carbonaceous chondrites, such as Murchison, which fell in Australia in 1969, contain clay minerals that formed in water, along with a few per cent carbon, much of it in complex organic molecules. Others hold tiny diamonds, minerals never found naturally on Earth and grains of dust older than the Sun itself.
Overall, the most primitive meteorites have a composition remarkably close to that of the Sun, minus gases such as hydrogen and helium. That is why scientists treat them as the raw ingredients from which the rocky planets, including Earth, were assembled.