ABSTRACT
Despite the large number of studies on the chemistry of gold, several of its compounds still remain unexplored. Chemists have long paid attention to the linear double-co-ordination compounds of Au(l), neglected the straight co-ordination compounds of Au(lll), almost left aside the compounds of Au(l and III) with much higher co-ordination numbers, and practically ignored the compounds of Au(ll) and Au(V). Thus the mineralogy of gold has been supplemented over the last 20 years with information on many of its new compounds with sulphur, oxygen, selenium, tellurium, bismuth, antimony and arsenic. In many cases new minerals of gold have been encountered as fine reaction fringes around native gold or its tellurides. The purity of gold and the degree of ordering of its alloys with silver depend on several physical and chemical factors: temperatures and their gradients during crystallisation, redox conditions, acidity-basicity of solutions and the ratio of the activities of the constituents.
