Unlike rocks, all minerals and are expensive, are difficult to get occur naturally, have a fixed chemical composition contain metal, dissolve in acid fracture, contain silica

Occur naturally, have a fixed chemical composition

All minerals contain one or more elements, which are pure substances that cannot be broken down into simpler substances by chemical means.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.