What property characterizes a mineral?

Minerals are defined by having a definite chemical composition, which means that they consist of specific, identifiable chemical formulas that determine their structure and properties. This attribute is essential because it allows scientists to categorize minerals based on their chemical characteristics, which in turn influences their behavior, formation, and the environments in which they can be found.

For example, quartz is a mineral made entirely of silicon dioxide (SiO2), which gives it consistent characteristics across different samples. This contrasts with materials that do not have a consistent chemical makeup, such as rocks—which can be composed of varying minerals in different proportions.

The other choices highlight misconceptions about the nature of minerals. Minerals are solid and cannot be liquid, they are not exclusively organic in composition (most minerals are inorganic), and while some minerals are formed from volcanic activity, many others form through different geological processes, such as sedimentation or metamorphism. Thus, having a definite chemical composition is the fundamental property that truly characterizes what constitutes a mineral.