Question

1. a is defined as a naturally occurring inorganic solid with a specific chemical composition and usually a crystalline structure. 18. rocks are classified into three main groups: , , and .

Explanation:

1. By the standard geological - mineral definition, a mineral is a naturally occurring inorganic solid with a specific chemical composition and usually a crystalline structure.
2. Geologically, rocks are classified into igneous, sedimentary, and metamorphic rocks based on their formation processes.

Answer:

1. Mineral
2. Igneous, Sedimentary, Metamorphic