Yorkstone is sedimentary sandstone formed more than 300 million many years back in the Carboniferous period of time as silt deposited by rivers, and is composed of quartz, mica, feldspar, silica, clay and iron oxides. It was very first quarried in Yorkshire in medieval times and by the 18th century a big business had developed quarrying the Yorkstone of the millstone grit and coal actions in West Yorkshire. The very first quarries or 'delves' were formulated in the outcrop on the valley sides an