HANDBOOK OF THE METEORITE COLLECTIONS. 



203 



entirely absent from these portions. The surface markings are of 

 three kinds : First, those which appear like original conchoidal frac- 

 tures, the sharp angles of which have been reduced by corrosion; 

 second, a series of shallow pits and grooves which are distributed 

 fairly uniformly over the entire surface except the flattened portion 

 mentioned; and, third, a very fine stipple-like pitting which gives 

 the surface a shagreen-like appearance. This shagreen effect with 

 numerous small, nearly circular, shallow pits occurs also on the flat 

 areas where the larger groovings are lacking as already stated. Thin 

 sections under the microscope show a faint smoky glass almost com- 

 pletely isotropic, but with an occasional minute, colorless, doubly 

 refracting point too small for satisfactory determination. A pecu- 

 liar series of anastomizing cracks much resembling the crackle struc- 

 ture on certain porcelain glazes, traverses the section in all directions. 

 The composition of this glass, as shown by an analysis of a portion 

 cut from the larger of the specimens, is given in column I below. In 

 columns II to IV are given analyses of tektites, as they have been 

 comprehensively called, from Tasmania, Australia, and Bohemia. 



Anabases of Tektites. 



I. Obsidian pebble. Analyst, J. E. Whitfield. 



II. Obsidianite. Upper Weld, Tasmania. Analyst, W. F. Hillebrand. 



III. Obsidianite. Near Hamilton, Victoria. Analyst, G. Ampl. 



IV. Moldavite. Tribitsch, Bohemia. 



Although data are lacking regarding the mode of occurrence of this 

 Colombian material, it is at once evident that it is a not unusual type 

 of terrestrial obsidian. 



(2) Obsidian pehhles, Clifton, Arizona (Cat. No. 53676).— These 

 pebbles were received at the Museum in 1899 from Frank Keppler. 

 There is apparently no question but what they are water-worn and 

 corroded pebbles of ordinary obsidian. They are dark, smoky black 



