Diamond crystallization in the Cu-C system is studied at high pressure high temperature conditions of 7.0 GPa and 1500–1800 °C. The minimum temperature of diamond synthesis by spontaneous nucleation is found to be 1800 °C. Diamond layers of optical quality are grown on the seed crystals via the chemical-potential difference method. From the infrared absorption measurements it is found that the diamond layers grown on the (100) faces of the seed crystals contain nitrogen impurities in the form of A centers with concentration from 700 to 1100 ppm and show strong hydrogen-related absorption peak at 3107 cm− 1. A number of specific optical centers are found in photoluminescence spectra recorded for diamond layers grown on both (100) and (111) faces of the seed crystals. The newly observed 1.748 eV center is tentatively assigned to defects involving Cu impurities. The 1.787 eV center is suggested to appear preferentially in diamonds with high contents of nitrogen and hydrogen impurities.