Minerals rocks and minerals

Quartz is the most useful single mineral in field identification, not because it is interesting to look at but because of what its hardness does to everything else. At 7 on Mohs' scale it si

Orthoclase is the alkali feldspar — potassium aluminium silicate — and it is the mineral responsible for the pink colour of most granite. Its name means "right-angle fracture", referring to

Calcite is the reference mineral for hardness 3, the fizz in an acid test, and above all for cleavage — three perfect directions that break a crystal into rhombs and make calcite one of the

Pyrite is the mineral that built the phrase "fool's gold", and the deception works because pyrite genuinely looks metallic and golden in a stream bed. It is iron disulfide, the most common s

Halite is sodium chloride — table salt — and it is the one common mineral for which taste is a legitimate field test. It forms by evaporation, it cleaves into perfect cubes, and it is soft e

Galena is the main ore of lead, and it is one of the few minerals that announces itself by weight before you have looked at it properly. Pick it up and the density is startling — 7.6 grams p