142 THE MINERALS OF TASMANIA. 



comparatively large size, specimens occurring occasionally 

 nearly 6 inches in diameter. The pentagonal dodeca- 

 hedron is so characteristic of pyrite that it is known as the 

 pyritohedron. It is often found in sharply defined, highly 

 polished crystals. Many other modifications of crystallo- 

 graphic structure are well known, and they form a dis- 

 tinctive group. The auriferous pyrites is well known, and 

 is of considerable economic importance ; the gold is not 

 chemically combined, but in the form of minute particles, 

 as may often be detected by the aid of the microscope, 

 scattered throughout the substance of the pyrites, or 

 implanted in the lamellae. 



The auriferous variety occurs at Beaconsfield, Lsfroy, 

 Mathinna, and at the other reef gold-mining localities. Not- 

 able localities for the massive, granular, and sub-crys- 

 talline varieties are Mt. Read ; Dial Range, in extensive 

 bunches of crystals; River Forth; Mt. Kershaw, north of 

 the Pieman River ; Savage River ; and many other places. 



Interesting bunches of well-formed crystals have been 

 obtained at the Curtin-Davis Mine, in association with 

 tetrahedrite. At Heemskirk some rather fine crystals of 

 the pyritohedron habit have been collected, and numerous 

 other localities have afforded crystals of more or less 

 interest, but they are usually somewhat small. In the Mt. 

 Lyell copper-gold-silver mining district this mineral has 

 been discovered and mined in enormous quantities, the 

 most important being that operated upon by the Mt. Lyell 

 Company. It comprises a vast contact deposit — bounded 

 by quartz conglomerate and schist of doubtful origin — of 

 pyrite, containing small quantities of copper, gold, and 

 silver. The main body is apparently of oval form, 

 approximately about 900 feet in length by 700 fest in 

 width, and gradually lessening in bulk as depth is attained. 

 There are occasional enrichments, consisting mainly of 

 irregular masses of bornite and stromeyerite. At the Stir- 

 ling Valley, between Tullah and Rosebery, a deposit 

 occurs, with which are associated several bands of cubical 

 galena. The pyrite is for the most part granular, with 

 pockets of small, fairly-developed crystals. 



'' At the Federation Mine, Mt. Heemskirk, in a lode- 

 formation in altered granite, there occur very symmetrical 

 crystals. Striated cubes and smooth-faced or striated 

 pyritohedra are found as simple forms, and combinations 

 of both cube and pyritohedron are common. The extent 

 to which the two forms are represented in the combina- 

 tions is variable. All forms found at this locality are 



