ABSTRACT
Limestones and dolomites often form productive aquifers with favorable conditions for groundwater abstraction. The main minerals in these rocks are Ca-and Mg-carbonates which dissolve easily in groundwater and give the water its ‘hard’ character. Usually, the carbonate rock consists of recrystallized biological material with a high porosity and a low permeability. Groundwater flow is then restricted to more permeable fracture zones and karst channels produced by carbonate dissolution. Prolonged dissolution over periods of thousands of years may result in the development of karst landscapes and fantastic features in caves. Apart from the carbonate rocks that consist exclusively of carbonate minerals, sands or sandstones, and marls and clays may contain carbonate minerals as accessory minerals or as cement around the more inert grains.
