Synthetic atacamite or paratacamite in contact with pure water, cucl2 or nacl solutions at temperatures from 25 to 100 degrees c, at times up to 70 days, did not convert to the other polymorph. In various methods of preparation, the copper hydroxychloride formed as paratacamite where the cucl2 concentration was sufficiently small, and as a mixture with atacamite at higher concentrations. -- ICCROM