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Dug by hand. Crafted by heart. Fall 7, stand 8.
Five field tests classify most common minerals without a lab. Color is a clue. The test wins.
Jasper, chert, and chalcedony typically test 6.5–7.0.
Unglazed porcelain tile. Hematite: reddish-brown. Pyrite: greenish-black. Native gold: golden yellow.
Translucent edges: chalcedony and agate. Opaque: siltstone, argillite, dense chert.
Calcite veining often fluoresces white, yellow, or red. Inert silica typically does not.
Carbonates fizz. Silicates stay inert. One drop. Pack the bottle out. Never test a finished jewelry face.
Red & polychrome jasper — iron-oxide silica, conchoidal fracture, Mohs 6.5–7.0.
Golden & yellow jasper — limonite in cryptocrystalline quartz.
Chalcedony & agate — waxy luster, translucent edges; agate is banded.
Black chert, argillite, siltstone — opaque, often carbon-dark, no waxy luster.
Optical calcite — rhombohedral cleavage, double refraction, Mohs 3.0, vigorous fizz.
Galena — metallic, dense, cubic 90-degree cleavage.
Gold: golden yellow, no tarnish, nuggets or wires, Mohs 2.5–3.0, golden streak, malleable, SG 19.3.
Pyrite: brassy, cubes, Mohs 6.0–6.5, greenish-black streak, brittle, SG 5.0.
Chalcopyrite: brassy to peacock, massive or tetrahedral, Mohs 3.5–4.0, brittle, SG 4.2.
Arsenopyrite: silver-white to steel grey, tabular, Mohs 5.5–6.0, grey-black streak, brittle, SG 6.0.