Here we report the high-pressure and high temperature synthesis of nanocrystalline diamond (NCD) from glassy carbon balls using a multianvil apparatus. Different chemical compounds were used as the synthesis and pressure transmitting media. A detailed characterization of the synthesized products was performed using optical microscopy, Raman spectroscopy and scanning electron microscopy (SEM). Fully optically transparent nanocrystalline diamond micro-balls and lenses with complete optical transparency and the size of about 15-40 mu m were synthesized at a static :pressure of 18 GPa in the temperature range of 1850-2000 degrees C using MgO as a pressure medium. (C) 2014 Elsevier B.V. All rights reserved.