 Metastable digenite forms on cooling from 73 °C.It appears to be isometric with space group Fdm and a=27.85 Å.This symmetry, however, is due to twinning of fine domains with rhombohedral symmetry, trigonal -3m, point group R-3m, a = 3.92 Å, c = 48 Å, Z =15 for formula Cu1.8S.