208 C. D. SMITH AND L. A. COTTON. 



proportion of flat orange-yellow transparent crystalline plates, 

 some of these, while quite transparent in the centre, were lemon 

 coloured and translucent on the edges. 



" The greater part of the sample was made up of flat crystalline 

 plates, the colour varying from orange-yellow to lemon-yellow, 

 the lemon-yellow parts being only translucent, but the orange 

 coloured parts more or less transparent. Some crystals were 

 dark and opaque in parts, and this was found to be due to an 

 inclusion of carbonate of lead. 



"There were just a few other crystals of even lemon yellow 

 colour and of different crystalline habit, the specimens showing an 

 uneven crystalline surface, quite distinct from the flat smooth 

 crystals mentioned above. It was these crystals which were found 

 in the previous sample. 



"Two lots of crystals were selected for analysis, the first lot 

 being more or less orange coloured, and the second lot all lemon 

 coloured crystals. The analysis gave 168 per cent, and 227 per 

 cent, of tungstic acid respectively, the lot with the more lemon 

 colour thus showed the more tungstic acid. 



"An analysis was then made on a carefully selected lot of the 

 clear transparent orange coloured flat plates. These had a hard- 

 ness 3 to 3 J, and specific gravity 7 05. The analysis showed 

 Tungstic acid (W0 3 ) .. ... trace 



Molybdic acid (Mo0 3 ) ... 395 % 



Lead oxide (PbO) 59-8% 



proving these crystals to be molybdate of lead. The analysis 

 corresponds approximately to the formula PbMo0 4 . 



"Two lots of the lemon coloured crystals with uneven crystalline 

 surface were then picked. These had a hardness 3 to 3J and 

 specific gravity 7*30. The analysis showed 



(a) (b) 



Tungstic acid (WO s ) ... 23-5 % 21-1 % 



Molybdic acid (Mo0 3 ) ... (lost) 22-0 



Lead oxide (PbO) ... ... 54-0 51-5 



"This analysis (b) corresponds approximately to the formula 

 3 PbW0 4 , 5 PbMo0 4 ." 



