The basic building blocks of all rocks, minerals, liquids, and
gases are chemical elements, which are made up of various
combinations of atoms. For example, when lead atoms combine with
sulfur atoms, the mineral galena is formed. A mineral is a
naturally occurring solid with a definite chemical composition
and crystal structure. Rocks are naturally occurring solids
composed of one or more minerals. Rocks are identified by the
minerals they contain and are grouped according to their origin
into three major classes: sedimentary, igneous, and metamorphic.
Each group is subdivided on the basis of texture and mineral
composition. Most of the rocks found in Kentucky are
sedimentary. Sedimentary rocks are formed from (1) the
weathering and transport of pre-existing rocks and (2) the
chemical precipitation of sediments. Examples of sedimentary
rocks are limestones, sandstones, and shales. Igneous rocks
result from the cooling of molten rock or magma to create rocks
like granites, basalts, and rhyolites. Metamorphic r