The "Meteorwrong" Problem
Meteorite hunters and enthusiasts frequently discover that the rock they were convinced had fallen from space is, in fact, entirely terrestrial. These false positives are so common in the community that they've earned a nickname: meteorwrongs. The good news is that a methodical approach using a few simple tests can quickly eliminate most candidates — and occasionally confirm something genuinely extraordinary.
Step 1: The Magnet Test
The single most useful quick test is checking whether a rock responds to a magnet. The vast majority of meteorites — including all chondrites, most iron meteorites, and many achondrites — contain metallic iron-nickel and will attract a strong magnet. Use a neodymium (rare earth) magnet rather than a weak fridge magnet for best results.
Important caveat: Many terrestrial rocks also attract magnets (magnetite-rich basalts, for example), so a positive result is necessary but not sufficient. A negative result, however, makes it very unlikely you have a meteorite.
Step 2: The Streak Test
Drag your specimen firmly across unglazed white ceramic (the back of a bathroom tile works well). Meteorites generally leave no streak or a faint grey metallic streak. A reddish-brown streak strongly suggests terrestrial iron oxide minerals — a common fool. Pyrite ("fool's gold") leaves a black streak and is not a meteorite.
Step 3: Look for Fusion Crust
Fresh falls are often coated in a thin, dark, glassy fusion crust — the result of the outer surface melting during atmospheric entry. It typically looks like a thin black or dark brown enamel coating, sometimes showing flow lines. Be aware that:
- Fusion crust weathers away over time; older finds may lack it entirely
- Some volcanic rocks (particularly basalt) can superficially resemble fusion crust
- Oriented meteorites may show regmaglypts (thumb-print-like depressions) on the crust
Step 4: Examine the Density
Meteorites are generally denser than terrestrial rocks of similar size. You don't need precision equipment to notice this — a palm-sized meteorite will feel noticeably heavier than a similarly sized piece of granite or limestone. Iron meteorites in particular are strikingly dense (roughly 7–8 g/cm³ compared to ~2.7 g/cm³ for typical crustal rocks).
Step 5: Cut or File a Corner
If your specimen has passed the above tests, filing a small patch or cutting a corner (with permission, if it's a genuine candidate) can reveal diagnostic internal features:
- Chondrules — Small spherical structures visible in the cut face of stony chondrites
- Widmanstätten pattern — A criss-cross crystalline pattern visible in polished and etched iron meteorites, unique to slow-cooled metallic cores
- Metal flakes — Bright metallic iron-nickel flecks within a silicate groundmass
Common Imposters to Rule Out
| Rock/Mineral | Why It's Confused | How to Eliminate It |
|---|---|---|
| Slag/industrial waste | Dark, heavy, bubbly texture | Vesicles (bubbles) — meteorites rarely have these |
| Magnetite-rich basalt | Dark, attracts magnets | No metal flakes on cut surface; lower density |
| Pyrite nodules | Heavy, metallic lustre | Yellow colour; black streak; brittle |
| Hematite concretions | Rounded, dark, heavy | Red-brown streak; not magnetic enough |
Getting a Professional Opinion
If your rock passes all the above tests, the next step is professional verification. Options include:
- University geology or planetary science departments — Many have staff willing to examine potential meteorites
- Natural history museums — Institutions with meteorite collections often offer identification services
- The Meteoritical Society — Maintains the Meteoritical Bulletin Database and can direct you to accredited researchers
- Online communities — Forums such as Meteorite-List and dedicated subreddits have experienced collectors who can provide initial assessments from photographs
Remember: a genuine meteorite find — however small — has scientific value. Document it thoroughly with GPS coordinates, photographs before and after any cleaning, and notes on how it was found before submitting it for analysis.