A sintered, generally spherical ceramic body, having an alumina content of from about 52 to about 55 weight percent distributed substantially homogeneously throughout the body, a silica content from about 32 to about 38 weight percent distributed substantially homogeneously throughout the body, an apparent specific gravity of about 2.61 to about 2.65, and a bulk density of about 1.45 to about 1.56 grams per cubic centimeter.