Process for making ceramic spheroids

Claim 1

A process of making ceramic spheroids comprising the following steps: (a) mixing and converting to spheroids, with the aid of water, raw materials comprising: 50 to 99.8 parts by weight of a mineral particulate comprising a ceramic mineral which has a fired density of less than about 2.9 grams per cubic centimeter when fired above about 1100° C. and includes at least one mineral having chemically bound water or sulfur, in a form which is not substantially water soluble, in amounts sufficient to yield 0.5 to 5.0 weight percent water or 0.04 to 2.0 weight percent sulfur in the total mass of mineral particulates; 0.1 to 50 parts by weight silicon carbide; and 0.1 to 15 parts by weight binder characterized by adhering the raw materials together into unified masses after their conversion to spheroids but before firing; (b) drying the wet spheroids from step (a); and (c) firing the dry spheroids from step (b), in contact with a parting agent comprising a particulate selected from aluminum oxide, magnesium oxide, and their precursors, at a sufficiently high temperature and for a sufficiently long time to form a shell, containing parting agent, on the ceramic spheroids, said fired ceramic spheroids having a fired density less then about 2.2 grams per cubic centimeter.