Abstract: Process for making particulate ceramics having an alumina rich region near their surface, comprising the following steps:(a) mixing and pelletizing, with the aid of water, raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;(b) drying the wet pellets from step (a);(c) mixing the dried pellets with alumina parting agent; and(d) firing the mixture of pellets and parting agent at a sufficient temperature (less than 1450.degree. C.) and for sufficient time for vitrification to occur.

Abstract: A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by:(i) a concentration gradient of alumina which increases from very low in the center to relatively high near the surface of the particles;(ii) a fired density less than about 2.9 g/cc; and(iii) closed cell microporosity.Certain embodiments of the inventive ceramic particulate are also characterized by a Krumbein roundness of at least 0.8 and are chemically stable.The ceramic is made by a process comprising the steps of:a. mixing and pelletizing, with the aid of water, the dry raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;b. drying the wet pelletizer product;c. mixing the dried pellets with a parting agent; andd.