DEAR DR. BLONZ: I wanted some information on the advantages of liquid colloidal mineral supplements. -- B.E., Hayward, CaliforniaDEAR B.F.: Colloidal mineral products are not new. The source of colloidal mineral supplements is usually clay or humic shale deposits. Unfortunately, there is no reliable published evidence to support claims of enhanced bioavailability from minerals in a colloidal form versus similar compounds in more standard supplement forms. Like vitamins, minerals are only needed in trace amounts, and they don’t provide any calories.