A method of the high-pressure high-temperature synthesis of single crystals of orthorhombic high-pressure boron B-28 from metal solutions is presented. The method is based on the high-pressure multi-anvil technique. The feasibility of single-crystal growth was demonstrated in a number of experiments conducted at various pressure-temperature conditions with various precursors including beta-boron of 99.99% purity and various metals (Cu, Au, and Pt) used as fluxes and capsule materials. It was found that after dissolution in metals at high pressures and high temperatures, boron crystallizes in the form of single crystals at low temperature. The process is accompanied by chemical reactions resulting in the formation of borides. The maximum length of the B-28 crystals achieved is similar to 100 mu m. (C) 2010 Elsevier B.V. All rights reserved.