Book 27, Question 95
How can you tell quartz from calcite?
They can look alike, but they behave differently.
Quartz is harder: it scratches glass and rates a 7. Calcite is softer, about 3, and can be scratched by a copper coin. Quartz breaks in smooth, curved pieces, while calcite splits into slanted blocks. A grown-up can also drip a little vinegar on calcite, which will fizz, but quartz doesn't react.