Meteors are made primarily of rock, metal, or a mix of both. The rocky portion is dominated by silicate minerals rich in iron, magnesium, silicon, and oxygen, while the metallic portion is an alloy of iron and nickel. The exact recipe varies depending on where in the early solar system the material formed, but these core ingredients show up again and again.
When a small body travels through space, it’s called a meteoroid. The bright streak it produces burning through Earth’s atmosphere is a meteor. Any piece that survives to reach the ground becomes a meteorite. Scientists study meteorites to understand what meteors are actually made of, since the composition is identical, just easier to analyze on a lab bench.
The Three Major Types
Meteorites fall into three broad families based on their makeup: stony, iron, and stony-iron. About 93% of all observed meteorite falls are stony, composed almost entirely of silicate minerals. Roughly 6% are iron meteorites, made almost entirely of iron-nickel metal. The remaining 1% are stony-iron meteorites, which contain roughly equal parts rock and metal. Stony-iron specimens are the rarest of the three groups and, because of the striking mix of translucent crystals embedded in bright metal, are often considered the most visually impressive.
These proportions reflect what actually arrives at Earth’s surface during witnessed falls. Iron meteorites are overrepresented in museum collections because their heavy, metallic appearance makes them far easier to spot on the ground and far more durable over time. Stony meteorites, by contrast, look a lot like ordinary Earth rocks and weather away more quickly, so many go unrecognized.
Stony Meteorites and Chondrites
The vast majority of stony meteorites are chondrites, a type that has barely changed since the solar system formed about 4.6 billion years ago. Chondrites get their name from chondrules: tiny, rounded or irregular grains typically between 0.01 and 10 millimeters across. These grains were once free-floating droplets of molten rock in the cloud of gas and dust surrounding the young Sun. Some cooled into perfectly round beads; others clumped together with neighboring particles before they fully solidified, giving them uneven shapes.
The minerals inside chondrules are mainly olivine and pyroxene, both silicates built from iron, magnesium, silicon, and oxygen. Tiny grains of metallic iron-nickel also appear inside and around the chondrules, sometimes up to a millimeter in size. Between the chondrules sits a fine-grained matrix, a mix of hydrated and water-free silicates, metal sulfides, oxides, and organic material. This matrix also contains rare presolar grains, specks of material that predate our solar system entirely.
One distinguishing chemical feature: stony meteorites contain far less silica than many common Earth rocks. If a rock’s silica content exceeds 60%, it is not a meteorite. Meteorites lack significant amounts of quartz, unlike granite and many other terrestrial rocks.
Chondrites also contain small, bright inclusions called calcium-aluminum-rich inclusions (CAIs). These are made of high-temperature minerals like spinel and perovskite and are thought to be among the very first solids that condensed in the solar nebula.
Carbonaceous Chondrites
A particularly interesting subgroup of stony meteorites is the carbonaceous chondrites. These are rich in carbon compounds and water, making them a window into the organic chemistry of the early solar system. They contain a diverse suite of soluble organic molecules: amino acids, carboxylic acids, sugar-related compounds, and even nucleobases, the building blocks of DNA and RNA. Water content in these meteorites can be orders of magnitude greater than the organic material itself, and that water played an active role in reshaping the minerals and driving chemical reactions inside the rock over billions of years.
Carbonaceous chondrites are significant for astrobiology because they demonstrate that complex organic chemistry doesn’t require a living planet. The amino acids and other molecules found in these meteorites formed through non-biological processes in space or on small, water-bearing parent bodies.
Iron Meteorites
Iron meteorites are almost entirely metallic, composed of two interlocking iron-nickel alloy phases called kamacite and taenite. Kamacite contains up to about 7.5% nickel, while taenite is much richer in nickel, ranging from 20% to 50%. The two minerals crystallized at different temperatures as molten metal cooled extremely slowly, likely over millions of years, inside the cores of small planetary bodies that later broke apart in collisions.
That slow cooling produced a unique internal pattern. When an iron meteorite is cut, polished, and etched with acid, interlocking bands of kamacite and taenite become visible in a geometric pattern called Widmanstätten figures. These patterns cannot be reproduced in a lab because they require cooling rates of just a few degrees per million years. Their presence is one of the most reliable ways to confirm that a chunk of metal is extraterrestrial.
Alongside the dominant iron-nickel alloy, iron meteorites contain minor amounts of troilite, an iron sulfide mineral that is rare on Earth and found almost exclusively in meteorites. Another trace mineral, schreibersite (an iron-nickel phosphide), and small pockets of graphite also appear in some specimens. Because of their tough composition, iron meteorites survive atmospheric entry and ground weathering better than any other type, and some of the largest meteorites ever recovered belong to this group.
Stony-Iron Meteorites
Stony-iron meteorites are the rarest class, making up about 1% of observed falls. They split into two main subtypes: pallasites and mesosiderites. Pallasites are the more famous of the two, consisting of gem-quality olivine crystals (the same mineral family found in peridot gemstones) suspended in a continuous matrix of iron-nickel metal. They likely formed at the boundary between the metallic core and rocky mantle of a differentiated asteroid.
Mesosiderites are messier. They contain roughly equal amounts of silicate rock and metal, but the two components are jumbled together rather than neatly separated. These are thought to have formed during violent collisions between asteroids, mixing core and surface material together.
Key Elements Across All Types
Regardless of type, the same handful of elements dominate meteor composition. Iron is the most abundant metal, present as free metal in iron meteorites and locked inside silicate minerals in stony ones. Oxygen, silicon, and magnesium are the other major players, forming the backbone of olivine and pyroxene. Smaller but still significant concentrations of nickel, chromium, manganese, sulfur, and calcium round out the list. These elements all occur at percent-level concentrations, meaning they make up a measurable fraction of the total mass rather than appearing as trace impurities.
The relative proportions of these elements in chondrites closely match the composition of the Sun (excluding hydrogen and helium, which are gases and don’t condense into rock). This is one of the strongest pieces of evidence that chondrites preserve the original solid building material of the solar system, essentially a sample of the dust from which planets, moons, and asteroids were assembled.
Minerals You Won’t Find on Earth
Meteorites occasionally contain minerals that are extremely rare or entirely absent in terrestrial rocks. Troilite, the iron sulfide mentioned above, is one example. While iron sulfide minerals are common on Earth (pyrite, for instance), troilite’s specific crystal structure forms only under the low-oxygen, low-pressure conditions of space. Schreibersite, an iron-nickel phosphide, is another mineral essentially unique to meteorites. Some researchers have proposed that schreibersite delivered reactive phosphorus to early Earth, potentially contributing to the chemistry that led to life.
Presolar grains found in chondrite matrices are perhaps the most exotic component of all. These microscopic specks of silicon carbide, diamond, and oxide minerals condensed in the atmospheres of dying stars before our solar system existed. They carry isotopic signatures that don’t match anything in our solar system, marking them as genuine interstellar material embedded in otherwise ordinary-looking rock.