564 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 63 



bonne-les-Bains in France were completely transformed to mammil- 

 lary limonite. 



Magnetite [Fere204], the black oxide of iron, probably occurs on 

 archeological iron more commonly than realized, especially on the inte- 

 rior of deeply corroded large iron objects where reducing conditions 

 are likely to prevail. There is a large technical literature in the rust- 

 ing of iron, but little that is available or useful to the archeologist 

 except in an excellent short summary given by Plenderleith in chapter 

 13 of his well-known work (1956) on the conservation of antiquities. 



IRON PHOSPHATE 



This class of compound seems to be getting some notice by archeologi- 

 cal chemists especially in England. The bright blue mineral which 

 is seen on iron artifacts recovered in certain wet clay soils is recognized 

 as vivianite, Fea (PO4) 2 * 8H2O. Leo Biek ( 1963 ) , chief of the Ancient 

 Monuments Laboratory in London, has shown the writer various frag- 

 ments of ancient iron and of waterlogged wood from archeological 

 sites stained blue by this mineral. Vivianite quite commonly occurs 

 also on nonartifactual organic material found in deeply buried archeo- 

 logical sites especially along river banks, and it testifies to the general 

 soil conditions that prevail there. Vivianite is colorless when freshly 

 uncovered in excavations, but quickly becomes blue in color when ex- 

 posed to air. Booth (1962) and coworkers in England have observed 

 the protective effect of vivianite coatings on iron nails which have been 

 exposed since the 16th century to normally corrosive soils. The com- 

 mercial use of phosphate salts in our time to protect iron from rusting 

 is well known. Also, some interesting observations on the role of 

 tannates and phosphates in the preservation of buried iron objects 

 recovered from clay deposits have been made by Farrer, Biek, and 

 Wormwell (1953) , investigators from the Ancient Monuments Labora- 

 tory. Both vivianite and oxidized vivianite were identified on a 

 Roman knife.^ It was also identified on an iron axhead excavated 

 from a crannog on Loch Glashan, Argylshire, Scotland.^ H. Barker 

 (1950) of the British Museum Laboratory has described the occurrence 

 of a dark brown hydrated ferric-phosphate accretion among the mate- 

 rials identified in the famous Sutton Hoo ship burial. It appears that 

 the phosphatic constituent was derived from the dissolution of cal- 

 cined bone in contact with iron artifacts. Tlie ferric phosphate ma- 

 terial was described as "amorphous" since it gave indefinite X-ray 

 diffraction pattern, and no mineralogical species was identified. 



There is little doubt that the familiar and well-ploughed field of 

 iron corrosion could be further examined with benefit to archeology. 



6 Private communication, R. M. Organ. 



