Kathleen M. answered 11/12/19
Lifelong Learner and PhD Scientist
You can identify different materials (or minerals) using several different properties, such as color (optical hue and transparency), hardness, how easily the mineral breaks, its crystalline structure, or type/degree of magnetism.
For example, traditional quartz is transparent, but so is diamond, however they have different crystal structures. Color is probably the most common initial identifier. Quartz can have several colors depending on the level of impurities. Some examples include amethyst (purple), citrine (yellow), and rose (pink).