The grains of a sedimentary rock may be cemented by mineral being deposited between them by percolating water over time It is the strength of the cement rather than the grains that governs the hardness of many sedimentary rocks Calcium carbonate (lime) and silica are two common 'cements'
Having a hard, brittle consistency because the particles are held together by cementing substances such as humus, CaCO3, or the oxides of silicon, iron, and aluminum The hardness and brittleness persist even when wet See also consistence