FLANGES OF AUSTRALITES (TEKTITES) 9 
of a and the anterior surface, & ; and the junction of flange and 
core, c. 
External Features 
The width of flanges (distance from chin to outer edge) usually 
ranges from 1 mm. to 6 mm., but Hodge Smith (1939) has recorded 
a button-shaped australite from Mt. Cameron, Tasmania, with a 
9 mm. flange. In circular and oval plate-shaped australites (Fig. 
2 w and x, and PI. I, 8 and 10) the flange forms the greater part 
of the specimens ; those from 8 mm. to 12 mm. across have flanges 
3 mm. to 5 mm. wide. Flanges are constant in width (PL III, 3) 
unless their outer edges are wavy (PL III, 2). 
Posterior surfaces of flanges on buttons and ovals have fine, 
concentric flow iJies in the chin region; those on most plate- 
shaped australites have radial flow lines. Circular or nearly 
circular bubble-pits and craters rarely interrupt the general 
smoothness of the posterior surfaces of flanges, although common 
on the posterior surfaces of cores. They are due to the bursting 
of gas bubbles at the surface as evidenced by the presence of a 
small blister about ready to burst on one of the flange fragments 
examined. Walcott (1898) suggested that the impact of small 
foreign bodies on semi -plastic australites caused the pits ; had this 
been so, remnants of such postulated foreign bodies, of which there 
is actually no evidence, should be found embedded in the pits. 
The anterior surfaces of flanges are continuous in curvature 
with the anterior surfaces of the cores (Fig. 1). Characteristic 
features are the flow ridges which are concentric or spiral (clock- 
wise or anti-clockwise) on the cores but wrinkled on some flanges, 
resulting in wavy outer edges unlike the smooth inner edges of 
flanges. Fine, radial flow lines are most marked in the troughs 
of the flow waves, and they also cut through some flow ridges. 
Bubble-pits on anterior surfaces differ from those on posterior 
surfaces in being often tube-like and parallel to the radial flow 
lines. In some instances, they emerge from beneath flow ridges 
situated near the junction of flange and core. Rare circular 
bubble-pits on anterior surfaces consist of a crater with a small 
cone-shaped elevation of glass at the bottom (Pl. I, 4) suggestive 
of collapse under air pressure rather than of bursting by 
expansion. 
In plan the shape of flanges corresponds with that of the 
australites on which they are developed, but in cross section 
they display considerable diversity of form (Fig. 2) and internal 
structure (PL I, 1). Fenner (1935) considered that no two 
