NO. 4 TEKTITE SPECIMENS — CLARKE AND CARRON 9 



susceptibility values depend both on the total amount of iron present 

 and the proportion of oxidized to reduced iron. The Martha's Vine- 

 yard and Georgia tektites contain approximately the same total iron 

 (table 4). The slightly higher proportion of oxidized iron in the 

 Martha's Vineyard tektite is consistent with the slightly higher mag- 

 netic susceptibility value observed for this specimen. The magnetic 

 susceptibility values for the Georgia and Martha's Vineyard tektites 

 fall in the range between the highest moldavite value Q.oxio -6 

 e.m.u./g.) and the lowest bediasite value (4.2 X io~ 6 e.m.u./g.) re- 

 ported by Sen f tie and Thorpe (1959). The zero magnetization value, 

 a value which is typical for tektites in general, is interpreted to mean 

 essentially complete solution of iron in the tektite glass. These ob- 

 servations are indicative of a history of high-temperature treatment 

 during formation of the glass. 



ABSORPTION SPECTRA 



The spectral transmission of a number of tektites, including the 

 Empire, Ga., specimen, in the ultraviolet, visible, and near infrared 

 regions of the spectrum (300 to 5,000 millimicrons) has been reported 

 by Stair (1955a, 1955b, 1956). Cohen (1958) has given absorption 

 spectra for a number of tektites in the region 300 to 2,600 millimicrons. 

 He points out that his curves and Stair's are in agreement for the 

 region they treat in common, and that the Empire, Ga., tektite curve 

 agrees particularly well with that of moldavites. Cohen (1958) in- 

 terprets these curves as being consistent with the high ferrous to 

 ferric iron ratio observed in chemical data on tektites (table 4), while 

 Stair (1955a) tentatively interprets them as indicative of high ferric 

 iron. 



A new determination of the absorption spectrum of the Empire, 

 Ga., tektite, along with that of the Martha's Vineyard spectrum, is 

 given in figure 2. These curves are directly comparable to those of 

 Cohen and were obtained by using a Cary Model 14 recording spec- 

 trophotometer. 5 Highly polished specimen slice surfaces were pre- 

 pared, using o- to 2-micron diamond powder followed by magnesium 

 oxide. 6 The Georgia tektite slice used for the photomicrograph in 

 plate 4, C and D, was further polished and used for the absorption 

 measurement. Masks with identical light transmission areas slightly 



5 Dr. Walter Shropshire, Jr., Division of Radiation and Organisms, Smith- 

 sonian Institution, did the instrumental work in obtaining these curves. 



6 Grover C. Moreland, Division of Mineralogy and Petrology, U. S. National 

 Museum, Smithsonian Institution, prepared the polished slices. 



