Abstract: A method for producing abrasive particles includes the following method steps: i. preparing a starting mixture containing at least aluminium hydroxide, which mixture can be converted at least into aluminium oxide by means of heat treatment; ii. extruding the starting mixture to form an extrudate; iii. separating the extrudate into intermediate particles; and iv. heat-treating the intermediate particles. The intermediate particles are converted into abrasive particles that contain aluminium oxide, and the extrudate and/or the intermediate particles is/are subjected to an input of energy that is asymmetrical with respect to the geometry of the extrudate and/or the intermediate particles.

Abstract: A method for producing abrasive particles includes: i) providing a starting mixture which contains at least aluminum hydroxide and which can be converted at least into aluminum oxide by a heat treatment, ii) extruding the starting mixture in order to form an extrudate, iii) separating the extrudate into intermediate particles, and iv) heat-treating the intermediate particles. The intermediate particles are converted into abrasive particles which contain aluminum oxide, and the starting mixture is pressed through at least one nozzle element with a plurality of substantially parallel nozzle channels. The nozzle channels are preferably arranged in a mutually spaced manner over the course of the extrusion process, and the extrudate has a spiral or hollow cylindrical shape at least in some sections.

Abstract: A process for the production of a gemstone arrangement comprising a plurality of gemstones which are held by a flexible carrier in receiving openings, and wherein the gemstones each have a setting surface and a visible surface and are so arranged in the desired arrangement or randomly distributed that the visible surfaces are on one side of a notional surface and the setting surfaces are on the other side of the notional surface, wherein a carrier material is applied in fluid form to the setting surfaces and between them and after hardening forms the flexible carrier.