Scale inhibiting particulates formed from a mixture of fly ash and a phosphonic acid curing agent; wherein the fly ash is cured into a solid material by the contact with the phosphonic acid curing agent. The mixture may also contain a multivalent ion and the particulates may be coated with a coating material in an amount from about 0.1% to about 40% coating material by weight of the scale inhibiting particulate to delay the release of the scale inhibitor.