Final answer:
Quartz is a mineral that is an inorganic, naturally occurring solid with a specific chemical formula (SiO2) and crystalline structure, making it one of the most common and recognizable minerals on Earth.
Step-by-step explanation:
Quartz is classified as a mineral. It meets all the criteria for being a mineral, as it is naturally occurring, inorganic, and exists in a solid form.
Quartz consists of silicon dioxide (SiO2) and is found in all types of rocks. It is the stable polymorph at the Earth's surface and forms six-sided crystals with a non-metallic luster, as indicated in Figure 2.4b. This mineral has a definite chemical composition and a characteristic crystalline structure.
Quartz is one of the most common minerals found in the Earth's crust and universally recognized for its hardness and the array of colors it can present due to impurities.