Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which characteristic defines minerals?

1. Natural organic compounds with variable structures

2. Inorganic compounds with homogeneous crystal structures

3. Always liquid at room temperature

4. Mixtures of different elements and compounds

The correct answer is: Inorganic compounds with homogeneous crystal structures

The defining characteristic of minerals is that they are inorganic compounds with homogeneous crystal structures. This means that minerals are typically formed through geological processes without the involvement of biological organisms, making them inorganic. The term "homogeneous crystal structures" indicates that minerals have a consistent and ordered arrangement of atoms, which is key to their identification and classification. Minerals can be recognized by their specific physical properties such as hardness, luster, and cleavage, which arise from their crystal lattice structures. This orderly and repeating arrangement of atoms leads to distinct shapes and forms in mineral specimens. In contrast, the other options describe properties that do not align with the definitions of minerals. For instance, organic compounds and variable structures do not pertain to minerals, and liquid states or mixtures are not accurate descriptions of mineral characteristics. Thus, the focus on inorganic origin and crystal structure is fundamental in defining what constitutes a mineral.