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Meteorite vs Slag: A Safe Look-Alike Screening Guide

Dark colour, unusual heft, and magnetic attraction do not prove that a specimen is a meteorite. Iron-bearing slag, magnetite-rich rocks, hematite concretions, and volcanic material are far more common look-alikes. The safest field approach is to look first for evidence against a meteorite—especially abundant bubbles through the interior, a red or black streak, or an industrial setting—then preserve any credible candidate for expert examination. Abundant rounded holes through a broken interior strongly favour slag or vesicular volcanic rock, not an ordinary meteorite. A thin fusion crust, unusual density, and magnetic attraction can support further investigation, but none confirms extraterrestrial origin. Do not cut or grind a promising specimen; document its find context and seek expert or laboratory review. Record the exact find location, date, surrounding material, and whether a fall was actually observed. Photograph every side with a scale before cleaning or testing. Inspect existing broken surfaces with a hand lens. Abundant bubbles throughout the interior strongly favour slag or vesicular terrestrial rock; do not create a new break merely to look inside. Bring a small magnet near the specimen or suspend it on a string. Record weak or strong attraction without dragging the magnet across a potentially valuable surface. Look for a thin coating that is texturally distinct from the interior. Do not label any black or glassy rind a fusion crust unless its thickness, boundary, and whole-specimen geometry agree. Avoid a streak test on a credible or valuable candidate. On an expendable fragment and only when ownership and safety permit, a red-brown or black streak supports terrestrial iron oxides rather than a meteorite. If several independent clues remain consistent, store the specimen dry in a clean container with its field notes and contact an appropriate museum, university, geological survey, or meteorite specialist for in-person assessment. A magnet test is a screening observation, not confirmation. Magnetite-rich rocks and iron-bearing industrial material are common and often magnetic. Do not cut, grind, drill, polish, acid-etch, or heat a promising specimen. Destructive testing can remove diagnostic surfaces, reduce scientific value, and create hazardous dust or sharp fragments. Industrial slag can contain sharp glass, metal, lead, arsenic, or other conta