144 



THE MINERALS OF TASMANIA. 



lead supplied by the alteration of lead sulphide. These 

 secondary minerals in their highest development are found 

 some distance from the actual outcrop. In pyromorphite 

 the phosphorus sometimes gives way to arsenious acid, 

 and by this change the mineral graduates to the chloro- 

 arsenate, or vanadic and chromic acids may act in the 

 same manner, and thus constitute the other members of 

 the group. The Sylvester Mine, at Zeehan, has afforded 

 the largest and most perfect crystallised masses of this 

 mineral so far obtained in this State. The crystals are 

 intricately interwoven, the normal colour being an intensely 

 dark-green. At the Godkin Mine, Wliyte River, it is found 

 in minute crystals, and as earthy pyromorphite in large 

 blocks, being in this condition mixed with clay, and at 

 times pyrolusite; in small veins with cupriferous pyrite 

 and galena in a quartz gangue at the River Lee. At the 

 Hercules Mine a limited quantity of attractive crystal 

 groups has occurred. At the Magnet Mine the crystals 

 are well developed, but usually somewhat small. The 

 colours vary at this locality in a remarkable degree, rang- 

 ing from milk-white to pale and dark green; again yellow 

 and shades of dark port-wine tint. It is found also 

 at many of the silver-lead mines of Zeehan, Dundas, and 

 the Heazlewood; but these minor occurrences do not need 

 special reference. 



•266. Pyrolusite (Oxide of Manganese). 



An abundant and widely distributed mineral, commonly 

 found in botryoidal, radiating, or granular masses, rarely 

 crystallised. It is black or bluish-black in colour, and is 

 much softer than psilomelane. 



Alluvial drift is often cemented into a compact mass by 

 ferro-manganei©, which is a mixture of this mineral and 

 limonite. Its more important localities in this island 

 are : — Penguin River, Heazlewood, Vale of Belvoir, Mt. 

 Claude, Zeehan, Dundas, Meredith Range, Pieman River, 

 Fingal, and the Dial Range. At the Balstrup Manganese 

 Hill Mine, at Zeehan, small crystals occur intermixed with 

 the more profuse radiated masses. 



267. Pyroxene (Bisllicate of Iron^ Magnesium, Calcium, 



dec). 



A petrologically important family of ferro-magnesian 

 rock-forming minerals, which are well represented in those 

 of igneous origin. They are divided into two well-estab- 

 lished groups, viz : — 



