FLANGES OF AU STRALITES (TEKTITES) 15 
have facetted surfaces (Fig. 3 0). Irregular flint-like particles 
(Fig. 3, H and J) are often associated with gas bubbles within 
their own substance and in the surrounding glass. Many bubbles 
were probably released during the formation of these particles. 
Other particles are ellipsoidal, some with flattened bases (Fig. 
3 M). The majority of those along the surface of union c are 
hemispherical (Fig. 3 N) ; they are embedded in the cores, and 
have their flat bases in contact with and parallel to c. 
Most of these particles are isotropic, but occasional irregularly- 
shaped examples (Fig. 3 H) are birefringent and give polarization 
colours of a low order but no axial figures; some such particles 
are surrounded by a halo of glass with a refractive index inter- 
mediate between that of the normal glass and that of the particles ; 
these haloes are usually isotropic, but a few are birefringent and 
give low polarization colours. 
Barnes (1940) regarded similar inclusions in bediasites 
(Texas) and other tektites as lechatelierite, i.e., re-fused quartz 
akin to the material of fulgurites ; he suggested that they indicate 
either limited liquid miscibility or, more probably, incompletely 
mixed re-fused quartz grains of the material from winch the 
tektites were formed. For this reason he suggested that tektites 
may be of fulguritic origin; but similar inclusions have been 
observed by the author in Pelee’s Hair from Kilauea, in Darwin 
Glass from Tasmania, and more rarely in fulgurites from 
Macquarie Harbour, New South Wales. 
The origin of these particles may be the key to that of tektites. 
Flow Structures 
Internal flow structures in cores and flanges are very pro- 
nounced (PI. I to III). Many near the posterior surfaces lead 
to the bases of bubble-pits (PI. II, 6 and 8), suggesting directions 
of internal gas streaming, but elsewhere they are associated 
with streaks of glass showing strain polarization, differences in 
refractive index, or both, and with elongated partially resorbed 
glassy inclusions. It therefore appears that flow lines result 
partly from escape of gas through the posterior surfaces and 
partly from flowage of molten glass. Directions of streaming 
are more readily determined in flanges than in cores. In flanges 
the spiral and elliptical structures are seen to best advantage on 
fractured surfaces (Baker, 1937, Figs. 1-7) and in radial sections 
(PI. I, 8 and 10, and PI. II). In equatorial sections of flanges 
these structures are concentric (PI III, 3 and 6), but within 
cores most of them are complex, their major directional trends 
