138 RKCORDS OP THE AUSTRALIAN MUSEUM. 



W. F. Petterd, of Launceston) a supposed new oxychloride of 

 lead, which was found in the upper workings of the Britannia 

 Mine, Zeehan, Tasmania, as groups of white hexagonal plates in 

 a quartz gangue containing disseminated pyrites ; the analysis 

 was made by Mr. O. E. White of Hobart.' Some time back Mr. 

 Petterd kindly lent me for examination his best specimen (PI. 

 xxxii.), also some detached crystals ; on a chemical and crystallo- 

 graphic study of this material the following conclusions are based. 



For a description of the physical characters I may refer to the 

 original account which is substgititially coiTect : no macles how- 

 ever were observed, and the hardness is not 1 -5 as stated, but 

 lies between 3 and 4, the mineral being harder than calcite and 

 softer than fiuorite. 



C rystaUoynxphy . Three crystals, each about -1 ram. in diameter 

 were measured on a two-circle goniometer. The angles obtained 

 are only approximate, as the faces are interrupted, wavy and 

 slightly cur^'ed, usually yielding only a vague patch of light in 

 the telescope. The basal plane is rough and gives no reHection, 

 therefore the crystals were centred by the prism faces. The 

 system is hexagonal, the forms present being c (0001), the 

 prism (lOlO), and the first and second order pyramids (lOll) and 

 (1121). Pyramidal faces do not occur on all the crystals and the 

 pyramid (1011) is the commoner and better developed. 



From the measurement 0001 A 1011=38° 42' the length of the 

 vertical axis was found to be "6938. The measured angle 

 0001 A 1 121 is 53° 20 ', calculated 54° 13'. 



Composition. In the endeavour to discover, if possible, the 

 affinities of this apparently new species, the original analysis 

 given below was more closely scanned. 



PbO ''4-04 % 



As., O, 2-60 



P,b, [sir] 2-10 



si).. O, -50 



CI 20-00 



99-24 



'I'o deduce a formula from these figures it is necessary to assume 

 an unlikely combination such as. — 



Pb--0^C1 O— Pb-Cl 



I or I 



Pb_0-Cl O— Pb-Cl 



' Twelvetrees— Kept. Secy. Mines Tas., 1900-1 (1901), p. 356, pi. ; 

 /rf.— Proc. ^oy. Soc. Tas., 1900-1 (1902), p. 51, pi. 



