202 BULLETIN 94, UNITED STATES NATIONAL MUSEUM. 



pittings on meteorites. In addition to this, the}' are dulled and ren- 

 dered opaque through abrasion from other stony particles, very much 

 like ordinary pebbles from the bed of a stream. In some instances 

 the}' are deeply cut or notched as in fig. 5. The colors are chrysolite 

 green, and the refractive index so high that they have in some 

 instances been cut and utilized as gems. 



The examples from Billiton (No. 77761), shown in pi. 41, figs. 1-3, 

 are much more remarkable both on account of their shape and the 

 extraordinary groovings which traA'erse the surface in all directions. 

 They are of a deep, lustrous black color and translucent only on the 

 thinnest edges. 



The Australian and Tasmanian occurrences have more the appear- 

 ance of water- worn pebbles which have been abraded by wind-blown 

 sand (Nos. 77611-12, 77525, and 88454, pi. 41, figs. 7-9). These are 

 also black and opaque excepting on the thinnest edges. In all, the 

 glass is wholly amorphous without trace of the trichites so character- 

 istic of obsidian and other volcanic glasses. A few characteristic 

 forms only are shown. 



Chemically, as will be noted in the selected analyses referred to 

 later, these forms are all acid glasses approximating in composition 

 the glassy forms of terrestrial rh3'^olites but unusually rich in lime 

 and magnesia. They are also remarkable for their small water con- 

 tent as indicated by loss on ignition, and their high fusing point. 



In none of the occurrences are the objects found in regions of vol- 

 canic rocks or under conditions which seem to render it at all likely 

 that they are of local derivation. It is seemingly impossible to con- 

 ceive of their having been ejected as volcanic bombs and drifted by 

 winds, and equally impossible, apparently, that they should belong 

 to either stream or glacial drift. An artificial origin is likewise con- 

 sidered impossible by the majority of those who have given the subject 

 consideration, and of late those who should be best qualified to judge 

 have been disposed to consider them as of a meteoric nature. 



In recognition of a possible doubt on this point, however, the 

 exhibit is accompanied by a small series of undoubted obsidian 

 fragments and pebbles which bear somewhat similar markings, in 

 some cases natural, in others produced artificially by means of fluor- 

 hydric acid. These are described below: 



(1) Obsidian pebbles froTn near Cali^ Defartmewt of Cauca^ Colom- 

 bia^ South America (Cat. No. 63471). — These were received at the 

 Museum from B. S. Hobbs through Dr. George F. Kunz, with the 

 simple labeling " Obsidian " from the locality above given. 



Two of the larger forms, it will be noted, are roughly spherical, 

 each showing on one side a flattened area as though it' had at some 

 time been attached to a larger mass or had remained in one 

 position during the etching process, since the larger grooves are 



