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Magnetite vs Hematite: Magnetism and Streak Guide

Magnetite and hematite are dense iron oxides that can both look black, gray, metallic, or earthy and often occur together. Pure magnetite is strongly magnetic and leaves a black streak. Hematite is usually not magnetic and always gives a red to red-brown streak, even when the hand sample looks steel-gray. Use both a magnet and a streak plate. Strong attraction plus a black streak supports magnetite. A red to red-brown streak supports hematite, even if included magnetite makes the specimen weakly magnetic. Test attraction with a small magnet before making a streak. Strong attraction is a major magnetite clue. Use a clean, unglazed porcelain streak plate. Black powder supports magnetite; red or red-brown powder supports hematite. Repeat the streak on more than one part of a coarse or banded specimen because both minerals may be present. Compare lustre and texture only after magnetism and streak. Metallic hematite can look deceptively similar to magnetite. Record the host rock and alteration. Mixed iron-oxide material may require microscopy or analytical work for a definitive modal estimate. Weak magnetism does not rule out hematite; included magnetite grains can attract a magnet. The red-brown streak is the more diagnostic hematite clue. Do not grind an unknown ore sample to make more powder. Minimize dust and follow occupational hygiene procedures. Magnetite or hematite does not establish ore grade or economic value. That requires representative sampling and analysis.