126 



THE MINERALS OF TASMANIA. 



width, and are occasionally remarkably small and propoi 

 tionately narrow. At the same time, it must be clearly 

 understood that there is no arbitrary rule as to form, as 

 intermediate shapes and sizes are to be met with, as well 

 as fragments of all sizes. The forms referred to can 

 usually be detected in fairly large collections of these 

 remarkable objects. 



The surfaces of the objects are often covered with shal- 

 low, extremely minute, pittings, which are probable gas 

 pores, and in rare instances are of comparatively large 

 size. Jn a few specimens the cavities are large and con- 

 spicuous. The surfaces also in rare instances, when the 

 preservation has been perfect, present clear and distinct 

 evidence of the irregular — at times curved — flow, as if 

 of a viscid substance, which has occasionally elongated the 

 pores or fittings referred to. A wonderfully preserved 

 elongated s^pecimen, of the dumb-bell type, from the 

 alluvial workings on the Purdue Mine, near Mt. Cameron^ 

 illustrates this in a marked degree. The specimen is abso- 

 lutely perfect, without any sign of abrasion. Thin sections 

 under the microscope show a pure glass, with minute 

 vesicles and unmistakeable optical evidence of irregular 

 strain and stress. 



They present from all localities a notable similarity in 

 physical characters. Although not unknown in the south- 

 ern portion of this island, the majority have occurred in 

 the northern part, perhaps owing to mining operations, on 

 the alluvial drifts, which have proved safe repositories 

 for these objects. 



On the mainland they have principally occurred in the 

 western portions of Victoria. They are reported to be 

 notably abundant throughout iSouth Australia in thie 

 central region. In middle and northern West Australia 

 they appear to be plentiful, more particularly about Kal- 

 goorlie and Coolgardie. In New South Wales they are 

 of somewhat rare occurrence, and from Queensland none 

 have been recorded. 



It is remarkable that they are not rarely obtained in 

 patches; for instance, in this State a batch of 17 was 

 collected within a restricted area a short distance north 

 of the Pieman Heads ; within another small area at Cam- 

 den, on the flank of Mt. Barrow, a patch or nest of nine 

 or ten was obtained in sluicing alluvial for gold. Nearly 

 60 years ago a parcel of above 50 specimens of various 

 shapes and sizes was collected at Mt. Talbot, County 

 Lowan. Western Victoria, and sent to the Hobart Museum^ 



