Reckitt's Crown Blue 740 gBluestone is an ingredient encountered in old time recipes for gamblers lucky hands and for floor wash used to purify the home. Also known as blue vitriol or blue copperas, bluestone is copper sulphate, a naturally occurring substance that is a highly toxic pesticide, and NOT SAFE to handle. Root doctors and spiritualists who want to work with the blue colour of copperas while avoiding its toxic side effects use crystalline LAUNDRY BLUEING SQUARES