Particles covered with a cured infusible thermoset film and process for their production

A process for the preparation of particulate matter coated with a cured phenolic resin wherein the improvement comprises mixing an uncured resin with particulate matter resistant to melting or decomposition at temperatures below about 450.degree. F., preheated to a temperature of from about 300.degree. F. to about 450.degree. F., adding with continued mixing from about 0.03% to about 0.5% by weight, based on the weight of the particulate matter, of a lubricant to the mix of resin and particulate matter and maintaining the resultant mixture above about 300.degree. F. for a sufficient time to cure the resin, whereby there is obtained a product containing individually coated particles having high abrasion resistance and improved crush resistance suitable for use as a propping agent in subterranean formations.