NO. 4 TEKTITE SPECIMENS — CLARKE AND CARRON J 



is also present on the Plainfield (pi. 5, C and D) and Osierfield 

 (pi. 6, B), Ga., specimens and can be seen in the photographs. 



Plate 6, A, is an enlargement of a small area of the surface of the 

 Plainfield, Ga., specimen. It shows several features that are common 

 to all the specimens with which we are concerned and one feature that 

 is peculiar to this specimen. The latter is an apparently glassy mass, 

 or protuberance, that projects from the bottom of a surface cavity 

 (pi. 6, A; and slightly to left of center in pi. 5, C). This protuber- 

 ance is firmly attached to the body of the specimen and apparently 

 resulted from chemical attack on a volume of glass containing an 

 inclusion or inhomogeneity of more resistant composition. No meas- 

 urements of properties or composition of this protuberance were 

 possible as the owner desired to maintain the specimen intact. 



All these tektites show what appear to be several generations of 

 surface pits, a feature particularly apparent on close examination 

 of plate 6, A. Around the top edge of the cavity containing the 

 protuberance there are four outlined depressions, apparently the rem- 

 nants of previous pits that have grown together and been largely ob- 

 literated by the younger central pit. The photograph also shows nu- 

 merous examples of pits within pits, and pits overlapping pits. A 

 particularly interesting pattern can be seen in the lower right-hand 

 corner of plate 6, A. A raised, rather white area is surrounded by 

 five distinctly outlined grayish areas that seem to have been formed 

 as a result of enlargement of pits. This feature and the glassy pro- 

 tuberance described above provide direct evidence that the internal 

 composition of the material has at least a limited control on the sur- 

 face features that develop. A number of very small pits possibly could 

 have resulted from bubbles within the glass, but it is impossible to 

 identify any of these from the photograph. 



To summarize: Study of the detailed morphology of these speci- 

 mens supports the idea that chemical weathering, controlled to a 

 slight extent by variations in composition of the material, is the main 

 agent responsible for the formation of these surface features. We 

 find no evidence either in the gross shapes or on the surfaces of these 

 specimens that suggests a history of aerodynamic shaping. 



PHYSICAL PROPERTIES 



A comparison of some of the physical properties of the two speci- 

 mens is given in table 2. All the properties listed are remarkably 

 similar. 



Density measurements were made by weighing the suspended speci- 

 mens in air and in carbon tetrachloride of accurately known density 



