Method for the work-hardening of diamonds and product thereof

A method of producing a free discrete work-hardened diamond crystal consisting essentially of the steps of:

• (a) filling an enclosure with a charge consisting of at least one free discrete diamond crystal wherein the largest linear dimension ranges in size from about 250 micrometers to about 5000 micrometers confined sufficiently in embeddment material and in direct contact with said embeddment material for application of pressure on said diamond crystal sufficiently uniform to substantially inhibit brittle fracture of said diamond crystal, said embeddment material being selected from the group consisting of diamond and cubic boron nitride having a size ranging from 1/10 to 1/100 of the largest linear dimension of said confined diamond,
• (b) subjecting said enclosure and said charge to the simultaneous application of pressure and temperature conditions located in the Region of Plastic Deformation as defined in the carbon phase diaphragm of FIG. 1 wherein the pressure ranges from 5 kilobars to 70 kilobars and the temperature ranges from 900.degree. C. to 1800.degree. C. for a period of time ranging from about one minute to 30 minutes whereby at least one face of said diamond crystal ranging in size from about 250 micrometers to about 5000 micrometers is work-hardened but whereby no significant bonding between said diamond and said embeddment material is produced, said work-hardened face, when polished, showing a plurality of straight bands elevated from said polished face, said straight bands being a manifestation of strain-hardened lamellae extending into the crystal and being composed of discrete work-hardened crystalline material, said work-hardened face having an abrasion resistance higher than that of a non-work-hardened face of said crystal, said work-hardened diamond crystal undergoing no significant bonding within said charge,
• (c) reducing the temperature to ambient,
• (d) reducing the pressure to atmospheric pressure, and
• (e) recovering the resulting free discrete work-hardened diamond crystal, said recovered free discrete work-hardened diamond crystal being at least significantly fracture-free.