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Mica vs Gold: How to Tell Glittering Flakes Apart

Weathered mica can glitter yellow or bronze and is a common source of false gold sightings in rock, soil, and stream sediment. Mica is a group of sheet-silicate minerals—including muscovite, biotite, and golden-brown phlogopite—so colour alone is unreliable. Look instead for mica's ability to split into thin flexible sheets and its pale streak. Native gold is much denser and malleable: an expendable grain tends to flatten, dent, or smear rather than peel into sheets or crumble. Use a hand lens on several grains. Mica shows one perfect cleavage and separates into very thin, flexible sheets; muscovite and common dark micas leave a white to grey streak. Gold does not peel into sheets: a suitable expendable grain bends, flattens, or dents and leaves a yellow streak. Treat sparkle and colour only as starting clues, and use an assay for any potentially significant occurrence. Record the location and photograph the unaltered material in diffuse light with a scale. Examine several grains rather than choosing only the brightest flake. Rotate the specimen under a steady light. Note whether reflections repeatedly switch on and off from flat parallel surfaces, which supports mica but is not conclusive by itself. Use a hand lens to look for stacked sheets, peeling edges, or thin translucent flakes. These are stronger mica clues than colour or sparkle. If a loose, expendable grain is available and testing is permitted, press it very gently with a pin on a clean hard surface. Record whether it flexes, springs back, separates into sheets, crumbles, or flattens without breaking. Use an unglazed streak plate only on expendable material. A white to grey streak supports common mica; a yellow streak supports gold. A black or greenish-black streak suggests another metallic look-alike such as pyrite or chalcopyrite. Use relative heft only as supporting evidence and only between similar volumes. A few paper-thin flakes are too small for a meaningful hand-heft comparison. For a potentially important occurrence, preserve representative material and field notes and use a qualified laboratory assay. A photograph or single field test cannot determine grade or economic value. Do not crush, grind, drill, heat, acid-test, or flame-test an unknown specimen. Dust and chemical reactions can be hazardous, and destructive testing can ruin useful evidence. Do not use mercury, cyanide, or other e