CORROSION OF METAL ANTIQUITIES — GETTENS 559 



[Pbs (CO3) CI2], from the same source and on a lead pipe in hot springs 

 from Bourbonne-les-Bains, France (1909). At the Laurion mines 

 in Greece this double salt of lead was found with laurionite and other 

 lead minerals formed by the action of sea water upon ancient slags 

 produced from smelting lead ores. Lacroix notes that only the 

 normal lead salts have been observed on the objects found in the 

 reducing environment of deep sea water off Mahdia, while at the 

 water's edge at Laurion the basic (oxy) salts predominate. A large 

 crystal of phosgenite was found by A. A. Moss* inside a metal 

 vessel, possibly pre-Roman in date, from the Great Cave, "Wookey 

 Hole, Somerset, England. The m.etal contained 60 percent lead and 

 40 percent tin. 



In the Freer Gallery study collection there is a stem or column of 

 an old Persian lamp which is made of highly leaded bronze. Most 

 of the surface is covered with nondescript corrosion crusts of copper, 

 but samples taken from scattered crystalline whitish patches give an 

 X-ray diffraction pattern of phosgenite. Also, on this same lamp 

 there were observed scattered small clusters of deep blue, highly re- 

 fracting crystals which X-ray diffraction analysis showed were made 

 of an even more rare mineral cumengeite [Pb4Cu4Cl8(OH)8], named 

 after the French mining engineer, Edward Cumenge ( 1829-92 ) . Only 

 a single occurrence from Baja California, Mexico, is reported in 

 Dana (1951). This is one more example of a rare mineral appearing 

 on an artifact. 



Other lead-copper minerals may occur, but they have not been 

 observed or reported. Here is a possible opportunity which should 

 not be overlooked by the archeological chemist or the rare mineral 

 collector. 



LEAD SULFATE 



An occurrence of white crystalline anglesite, PbS04, mixed with 

 galena on an ancient lead artifact from the thermal springs at 

 Bourbonne-les-Bains in France was reported by A. Daubree (1875). 

 Small deposits of anglesite mixed with phosgenite were observed by 

 G. Perinet (1961) on lead plates from the ancient sunken ship found 

 off Grand Congloiie. Anglesite probably occurs on lead artifacts 

 more commonly than is realized. 



TIN 



Tin is a metal of prime importance in archeology, not as an 

 individual craft material but as a necessary adjunct to the making 

 of bronze. Unfortunately, few objects of pure tin survive from 

 antiquity even from centers of early bronze making such as Egj^pt, 

 Mesopotamia, and China. If much pure tin was made in antiquity, it 



* Private commanlcation R. M. Organ. 



