Compacts are provided in which one or more single crystal diamonds, having a largest dimension of at least one millimeter, are embedded in the polycrystalline matrix which may be made of diamond; cubic boron nitride (CNB); and silicon and silicon carbide bonded diamond, CBN, or mixtures of diamond and CBN. The single crystal diamond is from 10-90 volume percent of the compact. The compacts (except for the silicon and silicon carbide variety) are made by high pressure-high temperature processing ...

The synthesis of diamonds from salts of iron, manganese, calcium and magnesium is disclosed. Specifically, such synthesis, in a closed system, has involved carbonate and oxylate salts of the indicated metals. The reaction occurs at temperatures between 550.degree. and 1600.degree. C., higher temperatures requiring higher reaction pressures; specifically, the production of synthetic diamonds from ferrous carbonate is disclosed. The ferrous carbonate was packed into a platinum capsule which was se...

In order to test whether a diamond has had a layer of synthetic diamond deposited thereon, it is irradiated with high energy ultraviolet radiation to cause emission of luminescence, the luminescence intensity produced by different zones of the diamond being measured and compared. In one embodiment an integrating enclosure (15) is used and the diamond (13) is mounted on a rotatable mount (14).

A diamond tool comprises a diamond (4) with a cutting edge (5) which diamond is encased in a sinter mass (7) which is brazed to the front end of a tool shank (1). The diamond (4) is brazed to a metal connection block (6) which is encased in the sinter mass (7) together with the diamond.

A diamond saw for cutting hard materials, in which a steel plate is fixed with a sintered abrading body consisting of diamond abrasive granules and a bonding metal powder, characterized in that a plurality of grooves are provided on the surface of both the front and back side faces of the sintered abrading body.

A method of reducing the color of diamond of type 1b including the steps of exposing the diamond to irradiation capable of causing atomic displacements in the diamond, for example the irradiation may be electron bombardment of energy greater than 300 KeV, followed by heat treating the irradiated diamond at a temperature in the range 1600.degree. C. to 2200.degree. C. under a pressure at which the diamond is crystallographically stable at the temperature used.

A brilliant gemstone cut, having a crown, a girdle and a pavilion. The crown has a flat table shaped as an equilateral n-sided polygon. The girdle is also multi sided polygon. The corner, lower girdle, bezel and star facets are at significantly angles of inclination, with respect to the table to provide significantly improved brilliance.The upper corner facets are spaced from the girdle. The space between the corner facet vertices and the girdle is left open to be covered by a prong of a jewelry...

Scratch-free polished diamond is obtained by rubbing a surface of the diamond to be polished against a smooth complementary diamond surface with sufficient pressure and velocity to heat the surface being polished above the spontaneous thermal degradation temperature of the diamond. Such a method can be used to burnish diamond-on-diamond bearings in as little as ten minutes as compared with up to three weeks by prior polishing techniques. Excessive thermal degradation of the diamond is avoided by...

A proposed diamond cutter is provided with man-made diamond grains on the circumference of a disc base plate, and is formed with slits from the outer circumference to the central part thereof. The slit is angled about 30.degree. with respect to a radial direction of said plate, so that the heat caused during cutting is prevented from running toward the central part, thereby to save the base plate from crackings. Minor cutting edges are also provided in addition to said angled cutting edge, and t...

A novel diamond disc is disclosed. The diamond disc comprises a plurality of diamond grains 2 bound on a disc. The diamond grains 2 are arranged in such a manner that a distance m1 between diamond grains 2 which are located on a common rotational track of the diamond disc and are located forward and rearward in a rotational direction R is set longer than a distance m2 between diamond grains 2 which are located on adjacent tracks in a radial direction so as to be close to each other.