Carbonates are minerals combined with carbon and oxygen,
including calcite, dolomite, smithsonite, malachite, and
cerrusite. Crystal system: hexagonal. Cleavage: three-
directional in rhombohedron-shaped fragments. Color: usually
white, but may be tinted various colors by impurities. Hardness:
3.0. Luster: glassy. Specific gravity: 2.71. Acid test:
effervesces strongly when treated with dilute hydrochloric acid.
Uses: in the form of limestone, as aggregate for road surfacing
and concrete, agricultural lime, flux, building stone, sulfur
sorbents, and in cement; in the form of Iceland spar in optical
instruments to obtain polarized light. Calcite is one of the
most abundant and widespread minerals in Kentucky. It may occur
in a multitude of crystal forms, of which scalenohedrons and
rhombohedrons are the most common; it may also be granular,
massive, earthy, or fibrous. Calcite is the chief mineral in
limestone, where it is generally in the form of small, broken
fragments of fossil shells. Large, well-developed