Diamond powder — also termed diamond dust or, when graded to coarser fractions, diamond grit — is finely crushed diamond abrasive sieved to precise micron sizes and used throughout the lapidary arts for cutting, grinding, lapping, and polishing gemstones. Because diamond occupies the apex of the Mohs hardness scale at 10, it is the only abrasive capable of working every gem species efficiently, including diamond itself. The material is produced from industrial-grade or synthetic diamond crystals, crushed and classified into standardised size fractions ranging from roughly 100 microns at the coarse end down to sub-micron grades (sometimes expressed as 0–0.25 µm) used for final mirror polishes on the hardest stones.

Production and Grading

Industrial diamond powder is manufactured either from natural bort — the irregular, low-quality diamond material unsuitable for faceting — or, increasingly, from synthetic diamond produced by high-pressure, high-temperature (HPHT) or chemical vapour deposition (CVD) processes. Crushing is followed by acid cleaning to remove metallic and graphitic contaminants, then wet or dry sieving and sedimentation to achieve tight particle-size distributions. Grades are typically expressed in microns (µm) or, in older trade usage, as mesh numbers corresponding to sieve aperture sizes. Common commercial grades include 100 µm, 60 µm, 45 µm, 30 µm, 14 µm, 6 µm, 3 µm, 1 µm, and 0.5 µm, with ultra-fine polishing compounds extending below 0.25 µm. Tighter distributions — sometimes labelled as monocrystalline or polycrystalline — affect cutting behaviour: monocrystalline particles fracture along cleavage planes to produce sharp new edges during use, while polycrystalline (blocky) particles are more self-sharpening and tend to produce smoother scratch patterns.

Forms and Carriers

Diamond powder is supplied and applied in several forms:

• Loose powder — sold in small vials or bulk quantities, mixed by the lapidary with a carrier fluid (water, oil, or proprietary extender) immediately before use on a lap or grinding surface.
• Diamond paste — powder pre-blended into a grease or oil-based carrier, dispensed from syringes in colour-coded grades for easy identification. Pastes are widely used for hand-lapping and polishing flat or curved surfaces.
• Diamond spray — a suspension in a volatile solvent, applied from aerosol cans to laps, wheels, or polishing cloths; the solvent evaporates, leaving an even distribution of abrasive.
• Bonded products — powder sintered or resin-bonded into grinding wheels, laps, core drills, and saw blades. These are technically distinct from loose powder but share the same raw material.

Lapidary Applications

In faceting, diamond powder on a metal or ceramic lap is the standard method for grinding and pre-polishing all gem species harder than approximately 7 on the Mohs scale, including corundum (ruby and sapphire, Mohs 9), chrysoberyl (8.5), spinel (8), and topaz (8). For polishing diamond itself — whether during the initial bruting and blocking stages or in final brillianteering — diamond powder on a cast-iron scaif (polishing wheel) remains the industry standard, exploiting the directional hardness variation between crystal faces. Cabochon cutters use diamond powder on flat laps and expanding drums for shaping and smoothing curved surfaces. In the carving and engraving of hardstone and gem materials, diamond powder suspended in oil is applied to rotary burrs and points. Softer gem species (fluorite, calcite, malachite) may be polished with finer grades of diamond powder or with alternative abrasives such as aluminium oxide or cerium oxide, though diamond powder produces consistently fine results across the full hardness range.

Selection and Use

Selecting the appropriate grade follows the same logic as any abrasive sequence: coarser grits remove material rapidly and eliminate scratches from previous machining steps; progressively finer grades reduce the scratch depth until the surface approaches optical smoothness. A typical faceting sequence for corundum might progress from a 260-mesh (approximately 60 µm) diamond lap for initial shaping, through 600-mesh (25 µm) and 1200-mesh (14 µm) pre-polish stages, to a 3 µm or 1 µm diamond paste on a tin, typite, or ceramic lap for the final polish. Contamination between grades is the most common source of persistent scratching; separate laps or thorough cleaning of the work piece and lap between stages is essential practice. The choice of carrier — water-soluble versus oil-based — depends on the lap material and the gem species: some porous or reactive stones (malachite, certain feldspars) are better worked dry or with minimal moisture.

Trade Suppliers

Diamond powder and paste are supplied by specialist lapidary and industrial abrasive companies. In the gemstone hobby and professional trade, suppliers such as Crystalite Corporation and United States Fused Quartz (USFG) have long offered standardised grades in vial quantities suited to the individual lapidary. Industrial suppliers — including Engis Corporation and Hyperion Materials & Technologies — serve the precision optics, semiconductor, and tooling industries with the same fundamental product at larger volumes and tighter tolerances. Pricing reflects both particle size (finer grades are more costly to classify) and crystal morphology (monocrystalline grades command a premium over blocky or irregular polycrystalline powder).