4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



anything that has been observed on Georgia tektites,* and it is an un- 

 common feature of tektites in general. The surface relief is also much 

 more pronounced for this specimen. It has sharp ridges on the top 

 and bottom surfaces and particularly on the serrated edge. These 

 sharp, relatively unabraded features imply that the Martha's Vineyard 

 tektite has not been transported far by normal geologic processes sub- 

 sequent to sculpturing. An unsual feature of this specimen is that the 

 edge pattern appears to be radial, while the surface pattern on the in- 

 terior of the disk appears to be concentric (pi. 3, A). 



There is a remarkable similarity between the Martha's Vineyard 

 specimen and a photograph of a moldavite published by F. E. Suess 

 (1900, pi. V, fig. 5b). Our specimen appears, at first glance, to be a 

 part of this specimen studied long ago by Suess. However, this ap- 

 parent duplication is due to the fact that Suess's photograph is en- 

 larged. His figures 5a and 5c show this tektite at natural size. It is 

 obvious that the Martha's Vineyard tektite must have come from a 

 parent of greater diameter than Suess's specimen. 



It has been stated above that the Martha's Vineyard tektite is ap- 

 parently a part of a larger disk-shaped object, probably 3 inches 

 (7.6 cm.) in diameter. If this assumption is valid, the parent body of 

 this specimen was larger than any disk-shaped tektite of which we are 

 aware. The hypothetical parent tektite would have a diameter-to-thick- 

 ness ratio of J.6, which is greater than that of any tektite known to 

 us. Even if a 2-inch diameter is assumed, this tektite would still have 

 a very high ratio, approximately 5. The Osierfield, Ga., tektite (pi. 6, 

 B, and table 1), with a ratio value of 7, is the only other tektite we 

 know of in this range. 



The internal structure and inclusions in the Empire, Ga., and 

 Martha's Vineyard specimens are shown in the accompanying photo- 

 micrographs. Plate 4, A, is a photomicrograph taken with white trans- 

 mitted light of a slice 0.25 cm. thick cut radially from the Martha's 

 Vineyard tektite. Plate 4, B, is of the same area using plane polarized 

 light, crossed nicols. Plate 4, C and D, are photographs of a slice 

 0.07 cm. thick of the Empire, Ga., tektite. If allowance is made for 

 the differences in thickness between the two sections, the similarity in 

 pattern and character of inclusions is apparent. Some of these inclu- 

 sions are well outlined and are of lower index of refraction than the 

 surrounding glass. They show wavy extinction and have not been 

 positively identified. Barnes (1940) has proposed that similar inclu- 

 sions in bediasites are lechatelierite. Sparsely distributed small round 



4 Bruce, G. A., personal communication, i960. 



