59 



ON THE OCCURRENCE OP SPHERULITIC FELSITE 



ON THE WEST COAST OF TASMANIA. 



By W. H. Twelveteees and W. F. Petteed, 



Bead November 15, 1897. 



Examples of this rock from four different localities have 

 come under our notice, namely, from Zeehan, the Castray 

 Jliver, Trial Harbour, and Strahan, and upon these occur- 

 rences we now offer a few observations. 



Zeehan. — Specimens broken from a loose boulder in a 

 swamp on the Montana Company's ground at Zeehan have 

 been handed about rather widely in the colony, and have 

 attracted attention from the exceptionally beautiful develop- 

 ment of spherulites in the substance of the rock. Well 

 preserved portions of these have been polished and used as 

 pendants and other ornaments. Speculations have been 

 made on the economic value of the iron-stained spherulites, 

 and altogether no small amount of curiosity has existed 

 respecting the nature of this handsome rock. The boulder 

 in question has been laid under such constant contribution, 

 especially recently, that only a few broken fragments now 

 mark the spot where it lay, and notwithstanding numerous 

 inquiries, we have been unable to hear of any similar rock 

 mass in the neighbourhood from which it may have been 

 derived. 



Macroscopically,the rock from Zeehan presents a dull milk- 

 white compact base, with numerous spherulites irregularly 

 scattered throughout its substance. The spherulites average 

 about five millimetres in diameter ; they are of a grey colour 

 with occasional splashes of a bright red, and have a glimmer- 

 ing glassy lustre. The specimens from the Castray River 

 are solid and somewhat granular throughout, with the 

 spherulites diffused with extreme irregularity. Occasionally 

 they form protuberances on the exposed surfaces, and, more 

 rarely, aggregates closely pressed together. The general 

 colouration of the rock varies from a dark grey to a rich 

 brown, the spherulites being equally varied in colouration. 

 Sometimes they are almost white, and by varied gradations 

 approach the darker shades of the general rock mass. Minute 

 patches of a bright red colour can be sometimes detected in 

 the vicinity of the marginal radiations, and a distinct nucleus 

 is often observable in the form of a small perforation or solid 

 core. That from near Trial Harbour is ajjparently of an 

 intermediate character in its general colouration and arrange- 

 ment of the spherulites, although it more closely approxi- 

 mates to the samples from the last mentioned locality. 



