BY W. F. PETTERD, C.M.Z.S. 89 



143. GuiTERMANiTE (Sulphide of Arsenic and Lead). 



A massive mineral occurs in the No. 1 south workings of 

 the Magnet Mine, which has much the physical appearance 

 of the above, and agrees with it as regards colour and 

 hardness ; but it is extremely difficult, if not impossible, to 

 isolate the pure material ; and the same applies to the 

 original guitermanite from Colorado. It is provisionally 

 placed under that species. It is bluish gray in colour, with 

 an obscure metallic lustre, always intimately mixed with 

 galena, sphalerite, and sometimes zinkenite. Upon being 

 struck it emits a strong odour of garlic. 



144. Gypsum (Sulphate of Calcium, or Selenite). 



This is not an abundant mineral as occurring in this 

 island. It is found at the Grunter Hill, Upper Mersey 

 River, as veins, occurring in blue limestone, and as radiating 

 masses of considerable size, which have an iridescent tar- 

 nish. It is also in limited quantity at Circular Pond 

 Marsh, near Gad's Hill. At Trial Harbour and some other 

 localities a small quantity has been noticed, while in 

 fractures in the dolerite rock at Launceston. minute crys- 

 tals occur rather plentifully. At Trefoil Island, off Cape 

 Grim, small irregular specimens, clear and translucent, 

 have been obtained. 



145. Halite (Chloride of Sodium). 



It would appear that some portion of the Mesozoic sand- 

 stone as exposed in the midland districts is constantly 

 saliferous, so much so that a restricted area is the source of 

 a permanent and apparently inexhaustible supply of chlor- 

 ide of sodium, or common salt. It has been collected in a 

 limited quantity for a lengthy period, and is locally used 

 for domestic purposes. No wholly, or even partially, solid 

 bed of salt has been discovered in this or any other portion 

 of the island. It is therefore highly probable that the 

 repeated renewal of the supply is derived from the sur- 

 rounding rocks, which are presumably saliferous. The 

 source of the mineral is a series of small lagoons or lakelets, 

 which contain saline water, or what are known locally as 

 the " salt pans." These are situated approximately 

 between Tunbridge on the south, and Ross on the north, 

 and comprise portions of the following estates, viz.: — 

 Lowe's Park, Ballochmyle, Ellenthorpe, and Mona Vale. 

 The so-called " pans " are at least ten in number, and are 

 in area from 1 to 100 acres. They extend in a south-east 



