Patent ID: 8235313

Claim:
A method of making spherical proppant having a selected grade from a naturally occurring, mined granular mineral having a hardness over 6 Mohs and having a particle size range where the maximum particle size is less than about 8.0 mm, said method comprising: (a) crushing said mined mineral into an intermediate particulate material; (b) screening said particulate material into a feedstock with particles having a particle size coarser than about 350 mesh and initial values for roundness and sphericity of the particles; (c) passing said particles of said feedstock through a blast tube with an outlet to pneumatically abrade said particles and propel said feedstock in a stream under a given pressure from said outlet; (d) directing said pressurized stream against a fixed target located at a given distance from said outlet to physically abrade said particles to form an output mass containing abraded particles; (e) repeating operations (c) and (d) a number of times or process stages until said particles resulting from said repeatedly abraded output mass is a final output mass having both processed roundness and sphericity values of at least 0.6 and wherein said values are greater than said initial values by at least about 0.10; and, (f) screening said final output mass to obtain a spherical proppant with said selected grade.