254 ANNUAL REPORT SMITHSONIAN mSTITUTION, 1942 



in seeking a reasonable explanation of their origin. The Australite 

 group of tektites adds still further probability to the cosmic theory by 

 showing a partial re-fusing of the original glass sphere, a part of 

 which has flowed backward and solidified into a more or less flat- 

 tened ring or band, giving to the whole specimen a peculiar buttonlike 

 appearance, in the typical forms. In many other cases, the re-fused 

 material has been completely swept away in flight, leaving only a 

 small sharp-edged or lens-shaped remnant of the original tektite 

 sphere. 



The Philippine tektites all belong to the general Indo-Malaysianite 

 group, of mid-Pleistocene origin ; this group contains also the tektites 

 found in Indo-China, Borneo, and the Island of Java. While present- 

 ing great uniformity in composition, and in color, specific gravity, and 

 other properties of the glass itself, the Indo-Malaysianites of dif- 

 ferent geographic areas present certain characteristic differences in 

 shape, surface markings, flow-lines, and the degree of viscosity of the 

 original material, which have led to their being divided into four 

 major and several minor subgroups of more or less distinctive and 

 well-defined character. The four major subgroups are: 



1. Indochinites (originally most viscous, with stretched-bubble sections, and 



with both straight and curved pointed drops, and irregular fragments 

 as the most characteristic forms, spheroids being rare). 



2. Rizalitea (pitted spheroids, ovals, and cylindrical forms being most char- 



acteristic, showing intermediate viscosity). 



3. Billitonites and Malaysianites (with deeply etched spheroids, cylinders, 



and Irregular pieces, showing worm-track grooves and navels as the 

 characteristic forms; medium viscosity). 



4. Java tektites (least viscous?, with highly complicated flow-lines mildly 



but clearly etched out on relatively smooth surfaces and with spheroidal 

 and irregular or fragmentary forms as the most characteristic). 



The most typical Indochinite specimens occur in South China and 

 northern and central Indo-China, although they are found also, 

 sparsely, in Luzon (particularly in the Rizal-Bulakan area, where they 

 are mixed with much larger numbers of Rizalites and a few Billitonite 

 and Malaysianite types). 



The most typical Rizalites occur only in Luzon, although a few 

 similar, pitted specimens are known from Borneo and Java. 



The Billitonite and Malaysianite types, although least in number, 

 cover the greatest area, being found in parts of southwestern Luzon, 

 the Island of Busuanga in the west-central Philippines, Borneo, the 

 Natuna Archipelago, southern Indo-China (especially Cambodia), the 

 Malay Peninsula, and the Island of Billiton. The original Billitonites 

 (first found in the tin mines of Billiton Island) show characteristic 

 worm-track grooves and navels, with relatively smooth surfaces be- 

 tween such markings, while the true Malaysianites tend to show ir- 

 regular and heavily etched surfaces with the irregular pits and other 

 markings often running together more or less continuously, as seen 

 most typically in many Cambodian and Busuanga tektites. 



