564 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1961 



adulterant and poor substitute for cinnabar. Cinnabar has often been 

 identified on Pompeian and Roman wall paintings. It was perhaps 

 known even earlier in China, where it was used for strewing graves, 

 and for filling the incised characters written on animal bones, now 

 called "oracle bones," which were used in Shang times for divining 

 purposes. Sometime about the beginning of the Christian Era, the 

 Chinese discovered a way to make cinnabar artificially, simply by 

 recombining mercury and sulphur, the elements of cinnabar, and 

 subliming the product to get the red modification of the sulphide. 

 This product, now called "vermilion," is purer and brighter than 

 natural cinnabar. The Chinese have used it since Han times for 

 making the red ink which is so often seen in the red seals stamped 

 on Chinese silk and scroll paintings, as well as for general paint 

 purposes. 



A number of important inorganic paint pigments that have no 

 counterpart in nature are derived from metallic ore and mineral 

 sources. In some instances, the natural substance is known, but is too 

 rare or too impure for commercial use. It is rather strange that no 

 usable chromium pigment is found naturally, although the mineral 

 chromite is the starting material for making several chromium pig- 

 ments including viridian (hydrous chromic oxide) and chrome yellow 

 (lead chromate) which came into use after 1800. No cobalt minerals 

 are directly useful as pigments, but the cobalt minerals smaltite, 

 erythrite, and asbolite have been used since prehistoric times to color 

 glass and ceramic glaze deep blue. The blue color is developed when 

 cobalt combines with complex silicates in the glaze at the high tem- 

 peratures attained in the pottery kiln. The skilled makers of glazed 

 porcelain of the Sung and later dynasties in China brought cobalt 

 minerals from as far away as Persia to decorate their beautiful blue- 

 and-white porcelain. In the Middle Ages, smalt, a kind of glass 

 colored with cobalt, was added to the painter's palette, and in the 19th 

 century three more cobalt pigments — cobalt blue (cobalt aluminate), 

 cobalt green (cobalt zincate), and cobalt yellow (cobalt potassium 

 nitrite) , all derived from cobalt minerals by chemical processes — filled 

 it out. 



Natural cadmium sulpliide, greenockite, is a rare mineral of no pig- 

 ment importance, but artificial cadmium sulphide made from cadmium- 

 bearing zinc ores is a rich and opaque stable yellow and is now a 

 mainstay of the artist's palette. 



The importance of the copper minerals malachite and azurite has 

 been mentioned. Artificial copper pigments made directly from cop- 

 per minerals also had their special uses. In Mesopotamia, as early 

 as the second millennium B.C., a way was discovered to make an arti- 

 ficial blue frit by calcining a mixture of lime, silica, and a copper 



