Caliche

Caliche is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, including in central and western Australia, in the Kalahari Desert in Africa, and in the southwestern United States. It is often used in construction in regions where it is abundant because it is strong and durable, and it is also used as a source of calcium for agricultural purposes and can be utilized in the production of cement.

Formation

Caliche layers form when minerals, especially calcium carbonate, precipitate out of water percolating through the ground. This process can occur at or near the surface to form a hard, cement-like layer. Caliche formation can be a slow process, taking thousands to millions of years, or it can occur relatively quickly in areas with high evaporation rates, where soil water moves upwards, carrying dissolved minerals which precipitate to form caliche.

Characteristics

Caliche is characterized by its light color, usually white to light brown, though the presence of other minerals can lead to various colors, including reddish or yellowish hues. It is hard and compact, making it difficult to excavate. The thickness of caliche layers can vary significantly, from a few centimeters to several meters, depending on environmental conditions and the length of time over which formation occurs.

Uses

In construction, caliche is valued for its stability and strength, making it a popular choice for building foundations, roads, and as a construction material in its own right. In regions where it is plentiful, it can be a cost-effective alternative to imported materials.

Agriculturally, caliche is mined for its calcium content, which is used to neutralize acidic soils. Its use in agriculture is especially common in areas where soil acidity is a problem for crop production.

In the production of cement, caliche can serve as a significant source of calcium carbonate, a key ingredient in the manufacturing process.

Environmental Considerations

While caliche can be beneficial for construction and agriculture, its extraction and use can have environmental impacts. Disturbance of land during mining can lead to habitat destruction and increased erosion. Additionally, the dust generated from mining and processing caliche can contribute to air quality issues.

See Also

• Sedimentary rock
• Calcium carbonate
• Soil stabilization
• Aridisol
• Mollisol