98 Z. V. Pirsson — Artificial Lava-Flow 



Morozewicz* lias also described crystallizations resulting 

 from tlie outHc)\viiig of glass from industrial furnaces ; in this 

 case large single crystals of wollastonite were formed. He 

 mentions also rounded aggregates of fibrous diopside, but does 

 not describe them definitely as of spherulitic structure. 



Spheruiites. — The most important kind of crystallization 

 shown by the Kane glass-flow is in the formation of spherulites. 

 The glass itself is an ordinary green bottle glass, pale greenish 

 where thin and a clear, sea-green wben a con pie of inches thick 

 or more. This is more or less filled with white spherical 

 bodies which vary in size from that of very fine shot up to 

 those which are neai-ly the size of an egg. These, and espe- 

 cially the largest ones, may be readily broken out of the glass, 

 either as single spheroids, or as grouped or botryoidal masses. 

 When extracted they have a sniootli. thin, outer shell of glass 

 -which covers them like a skin. These solid bodies when 

 broken open are white, with a pale greenish tinge, and are 

 seen to possess a fibrous radiated structure. The fibers are 

 extremely fine and thread-like, giving to the surface the luster 

 of" floss silk. This is true even in the largest. In some the 

 ci'oss section of the broken spherule, as it lies in the glass, 

 appears radial but uniform, while in others changes in the 

 conditions of crystallization, as the fibers grew outwardly fi-om 

 the center, have produced a series of concentric rings, such as 

 are sometimes observed in the smaller spherulites in rhyoliie. 

 As many as ten of these rings, of almost perfectly circular form 

 and of similar width, have been observed in one spherulite, 

 and, thus mottling the silky sheen of the surface of the section 

 of the divided spherulite, they have a moir^, or concentric, 

 watered-silk appearance, and add greatly to its beauty. The 

 structure, or consistency, of the spherulites varies greatly ; 

 some are so compact that they are composed almost wholly of 

 crystalline material, while in others the thread-like fibers are 

 relatively widely separated and the whole spherulite is satura- 

 ted with the greenisli glass. Thus, while the first form very 

 solid white objects, the latter appear almost like mist}' or cloudy 

 forms in the green matrix surrounding them, and the con- 

 choidal fracture passes through the glass without reference 

 to them nor can they of course be broken out and separated 

 from it. 



In another portion of the flow which formed a sheet about 

 two inches thick the spherulites have a somewhat different 

 character. Here they appear to be composed, not of tenuous 

 fibers, but of distinct, rather thick, blades, O'5-l-O""" broad by 

 ^mra long, as may be seen by reference to figs. B and C in 

 Plate I which represents them in very nearly natural size. 

 *Min. Petr. Mitt., xviii, p. 124, 1898. 



