Common Forms of Caliche

Caliche is a fairly broad term that describes sedimentary rocks containing secondary calcium carbonate found just below the surface in semiarid and arid environments. Caliche is the material that's left behind after ground water and soil moisture have evaporated and calcium carbonate (lime) leached. The original calcium carbonate can come from a number of sources including limestone, runoff from areas containing calcium carbonate, calcium carbonate-charged ground water, and even from calcareous airborne dust.

The most common forms of caliche include:

• Hard white or cream-colored nodules in the soil
• Thin white crusts found on pebbles and in crevices in soil or bedrock
• Thick, dense, rock-hard layers of sedimentary material resembling limestone. These thick layers of caliche are called calcrete. The size of calcrete layers can be anywhere from a few centimeters thick to several meters thick. Calcrete layers are typically found just below the surface of top soil from a few centimeters below to about two meters below the surface.

In addition to its various forms, caliche is referred to by several different names including: calcrete, hardpan, and duricrust. In India and Egypt, it's called kankar or kunkur while it's called croute calcaire in Tunisia.