Chemistry and mineralogy of some Lower and Middle Chalks from Givendale, East Yorkshire

Abstract

AbstractThe chemical composition of nine samples of Lower and Middle Chalk from the Givendale area of Yorkshire was determined; acetic acid residues were mechanically, chemically and mineralogically analysed. All nine chalk samples proved to be exceptionally pure calcium carbonate (96±1·5%), with only small amounts of MgO (1·03±0·53%), Al2O2 (0·33±0·28%) and Fe2O2 (0·20±0·14%). Insoluble residues ranged from 1·07 to 4·46%. Clay formed 56–88% of the insoluble residue. The non-clay fraction consisted of flint, quartz, collophane, limonite, feldspar, tourmaline and zircon. The clay fractions were dominated by montmorillonite (50%) with secondary illite (30%), apatite (3%), and quartz (8–30%). Kaolinite was detected by X-ray diffraction in the Lower Chalk.