AFOQT Practice Test

What defines a mineral?

1. A solid, organic compound with a defined structure

2. A naturally occurring, solid inorganic substance with a crystal structure

3. A liquid substance with varying chemical compositions

4. A synthetic material created in laboratory conditions

The correct answer is: A naturally occurring, solid inorganic substance with a crystal structure

A mineral is defined as a naturally occurring, solid inorganic substance with a crystal structure. This definition encompasses several key characteristics that are essential for classifying a mineral. Firstly, the term "naturally occurring" indicates that minerals form through natural geological processes, rather than being artificially manufactured. This rules out any man-made substances, which is important because synthetic materials, like plastics or lab-created gems, do not qualify as minerals. Secondly, the definition requires that a mineral is "solid." This means that minerals maintain a definite volume and shape, distinguishing them from liquids or gases. The option that describes a liquid substance contradicts this fundamental aspect, as liquid materials lack the rigid structure characteristic of minerals. In addition, the specification of being "inorganic" emphasizes that minerals are not derived from living organisms. While some might think of organic compounds (like those containing carbon) when considering substances that occur in nature, minerals strictly remain inorganic, thus excluding organic compounds or any materials that involve the biological processes of living organisms. The mention of a "crystal structure" is also vital. Minerals have a specific atomic arrangement that forms a crystal lattice, leading to unique physical properties, such as hardness, cleavage, and specific shapes. This characteristic further differentiates them from