Meteor-wrongs: the rocks that fool people
Most rocks sent to museums as possible meteorites are ordinary Earth rocks or industrial waste. Collectors call them meteor-wrongs. The commonest ones are heavy, dark, rusty or magnetic, which is exactly why they fool people. This gallery shows how to tell each of them from a real meteorite with simple, safe checks.
Try the rock checkerStep-by-step identification guide
Five quick checks
- Magnet
- Hang a strong magnet on a thread and bring it close. Most meteorites pull it clearly because they contain iron-nickel metal. Do not stick the magnet on: it can chip the surface, and scientists value a meteorite's natural magnetism, which a strong magnet can overprint.
- Streak
- Rub a corner on the unglazed back of a ceramic tile. Most meteorites leave little or no streak, or a faint grey one. A red-brown streak means hematite; a black streak usually means magnetite; a yellow-brown streak means rusty iron minerals such as goethite.
- Weight for size
- Meteorites containing metal feel heavy in the hand. Ordinary rocks have densities of about 2.6 to 2.8 grams per cubic centimetre, stony meteorites about 3 to 3.7, and iron meteorites about 7.5 to 8.
- Holes and bubbles
- Gas bubbles mean something once melted on Earth, such as slag or lava. Meteorites are solid; their surfaces have shallow thumbprint-like hollows, not round holes.
- The inside
- A small polished window on one corner of a stony meteorite usually shows bright flecks of metal and, in most cases, small round chondrules. Earth rocks show quartz, layers, crystals or nothing at all. Grinding is a job for an adult with eye protection.
The gallery
Slag
The glassy or stony waste left over from smelting metal ore. Slag heaps from old ironworks, foundries and mines are found across the industrial world, and slag was often spread on railway beds, farm tracks and roads.
Why it fools people: Slag can be dark, heavy, rusty and even magnetic if it contains iron, and its glassy skin can look like fusion crust.
How to tell:
- Gas bubbles, often round, on the surface and inside
- A glassy, shiny or flow-banded look on broken faces
- Often found near railways, old industrial sites and tracks
- No chondrules and no flecks of nickel-bearing metal inside
Bubbles and glassy breaks mean slag. Meteorites are not bubbly.
Magnetite
A black iron oxide mineral and an important iron ore. It is common as grains in many rocks and as dense black lumps and crystals.
Why it fools people: Magnetite is very heavy and attracts a magnet strongly, so it passes the two tests people try first.
How to tell:
- A black streak on an unglazed tile
- Grey-black and slightly metallic all the way through, with no shiny metal flecks when ground
- Sometimes shows small eight-sided crystals
- No fusion crust and no chondrules
Strongly magnetic plus a black streak points to magnetite.
Hematite
A red-brown to steel-grey iron oxide and the world's most important iron ore. It forms shiny grey masses, rounded 'kidney ore' and earthy red lumps.
Why it fools people: Hematite is dense and can look metallic or have a dark, crust-like surface.
How to tell:
- A red-brown streak on an unglazed tile, even when the rock looks grey
- Usually only weakly magnetic or not magnetic at all
- Rounded, bubbly 'kidney' surfaces or a radiating inside
- No fusion crust, no chondrules
A red-brown streak means hematite, whatever its colour.
Basalt and lava
Dark volcanic rocks made from cooled lava. Basalt is the commonest rock of the ocean floor and of many volcanic regions, and rounded basalt pebbles turn up on beaches and in rivers worldwide.
Why it fools people: Basalt is dark, fairly heavy and can weakly attract a magnet because it contains a little magnetite. Weathered surfaces can look like a crust.
How to tell:
- Small holes called vesicles, or tiny visible crystals
- The same dark colour inside as outside, with no thin crust
- Feels lighter than a meteorite of the same size
- No flecks of metal on a fresh face
Holes and an even dark interior mean volcanic rock.
Iron concretions
Rounded lumps that grow inside sediment as iron minerals cement sand or mud together, then weather out. They are often called ironstone nodules, and some are hollow.
Why it fools people: Concretions are round, rusty, dark brown and often surprisingly heavy, so they look like old weathered meteorites.
How to tell:
- A layered shell, like an onion, when broken
- Sand grains or mud inside
- A yellow-brown to brown streak
- Usually not magnetic
Layers and sand inside mean a concretion.
Industrial iron
Pieces of cast iron, steel and other man-made metal: broken machine parts, grinding balls from mills, ploughshares, horseshoes, cannonballs and lumps of furnace iron.
Why it fools people: Man-made iron is heavy, rusty and strongly magnetic, just like an iron meteorite, and it has been scattered across fields and beaches for centuries.
How to tell:
- Flat faces, straight edges, mould seams, holes or threads
- A rough, sandy casting skin rather than smooth thumbprints
- Little or no nickel: a nickel test on a ground spot stays colourless, though some alloy steels do contain nickel
- No Widmanstätten pattern when a slice is etched by a laboratory
Shapes made by people, or no nickel, mean industrial iron.
Chert and flint
Very hard rocks made of microscopic quartz. Flint is the dark form found as nodules in chalk, which is common in southern England and northern France; chert forms layers and nodules in limestone.
Why it fools people: Freshly broken flint is shiny black and smooth, and nodules have a pale skin that can look like a crust from the outside.
How to tell:
- Breaks with smooth, shell-like curved surfaces and sharp edges
- Light for its size and not magnetic
- A white or cream outer skin on flint nodules
- Glassy or waxy lustre inside, with no metal
Light, shell-like breaks and no magnetism mean chert or flint.
Obsidian
Natural volcanic glass that forms when lava cools too fast for crystals to grow. Small rounded pieces are sometimes sold as 'Apache tears'.
Why it fools people: Obsidian is jet black and glossy, like the fresh fusion crust on a new fall.
How to tell:
- Glassy right through, not just on the surface
- Very sharp, curved fracture surfaces
- Thin edges let light through, often brownish or grey
- Light for its size and not magnetic
Black glass all the way through means obsidian. Fusion crust is less than a millimetre thick.
Pyrite and marcasite nodules
Lumps of iron sulphide that grow in chalk, clay and coal. In southern England they weather out of the chalk and were once called 'thunderbolts' by people who thought they fell in storms.
Why it fools people: They are heavy, rounded, dark and rusty on the outside, with a strange knobbly shape.
How to tell:
- Broken open, they show brassy, radiating crystals from the centre
- Not magnetic
- A greenish-black streak
- Often crumble and smell of sulphur as they decay
Radiating brassy crystals inside mean an iron sulphide nodule.
Desert varnish
A thin, dark, shiny coating of clay, manganese and iron oxides that builds up on rocks in dry regions over thousands of years.
Why it fools people: Varnished desert stones look dark and glossy, like fusion crust, and they lie on the same open ground where real meteorites are found.
How to tell:
- The coating covers an ordinary light-coloured rock, visible on any chipped edge
- Usually only on the upper, exposed side
- Not magnetic unless the rock itself is
- Feels no heavier than any other stone
A dark skin over an ordinary rock is varnish, not a fusion crust.
Tektites are natural glass objects formed from Earth rock melted and thrown out by large impacts, such as moldavites from central Europe. They are linked to impacts, but they are not meteorites, because they are made of Earth material.
Work through the rock checker. If your rock passes most checks, take clear daylight photos next to a ruler, note exactly where you found it, and contact a natural history museum or university geology department. Do not cut, heat, wash or put acid on it, and children should leave any testing to an adult.
Related pages
- Can slag be mistaken for a meteorite?
- Are all meteorites magnetic?
- What is fusion crust and how do I recognise it?
- What does the inside of a meteorite look like?
Glossary: Meteorwrong, Slag, Magnetite, Hematite, Concretion, Fusion crust