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

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