ABSTRACT
Sedimentary, organic or chemical carbonate. Variable sized calcite mosaic, usually with shell fragments. Calcite 95%, dolomite 3%, clay minerals 2%. Marine shell debris and chemical precipitate, lithified by recrystallization. Uplifted and exposed by erosion, in folded or unfolded beds. Britain: Pennine dales. USA: Mammoth Cave Plateau. Massive or thin bedded; commonly with thin shale partings. May include large lenticular reefs of massive strong limestone. May contain nodules and lenses of silica: flint in chalk, chert in limestones, Soluble in rainwater, leaving minimal or no soil, and allowing formation of open fissures, sinkholes and caves. Forms distinctive karst landscapes with underground drainage dry valleys and commonly many bare rock outcrops. Karstic collapse into caves may occur, but as rare events; limestone gorges are common, but most are not collapsed caves. Older limestones are more completely recrystallized and stronger. UCS: 20-100 MPa. SBP: 0.5-4 MPa. Extreme variability; strong rock with open fissures and cavities. May shear along thin shale beds. Efficient aquifer with diffuse and conduit flow. Valuable dimension and aggregate stone. Burn with clay to make cement. Oolite: consists of sand-sized spherical calcite concretions. Chalk: weak, friable, pure, white limestone. Travertine, tufa: son, porous, banded calcite precipitated in flowing water. Dolomite: recrystallized with magnesium content (in dolomite mineral). Calcilutite: compact, strong, fine grained limestone.
