Geology and Natural History. 465 



ing of arsenic. No determination of arsenic was made in the 

 first analysis and its presence was evidently not suspected. Prior's 

 results are as follows : 



Pb, 68-49; Sb, 9-13; As, 4-59; S, 17-20; total, 99-41. 

 These results yield the formula 5PbS(Sb, As)2S3, which is the 

 accepted formula for geocronite. 



An analysis of Mieksite by Prior gave the following results : 



Atomic ratios. 



Ag 38-17 -353 or 4 



Cu._ 5-64 -090 " 1 



I 56-58 -446 " 5 



100-39 

 which yield the formula, 4AqI . Cul. The specific gravity of the 

 mineral was determined as 5-640. 



Marshite was also analyzed by Prior and gave the following 

 results : 



Atomic ratios. 



Cu 32-35 -513 



Ag 1-19 -Oil 



I 65-85 -520 



99-39 

 which yield the formula Cal. Specific gravity = 5*590. — Min, 

 Mag.^ xiii, 60. 



CooLGAEDiTE. — This mineral was discovered by A. Carnot at 

 Kalgoorlie. It is steel-gray to yellow-gray in color, is practically 

 devoid of cleavage and breaks with a conchoidal fracture. Its 

 formula is (Au,Ag,Hg)2Te3 and it is, therefore, related to colo- 

 radoite (Ilg^TCg) and melonite (Ni^TeJ. The following are 

 Carnot's analyses : 



I. II. III. 



Au 2315 27-75 37-06 



Ag 16-65 13-60 4-71 



Hg 3-10 3-70 3-70 



Cu -10 -25 -88 



Fe ._ trace trace -90 



Te 56-55 53-70 51-13 



Sb -20 -15 1-20 



Total 99-75 99-15 99-58 



— Geol. Surv. W. Australia^ Bull. No. 6, p. 1 8. 



CoLORADOiTE occurs freely and in large pure masses at Kal- 

 goorlie. A new analysis of pure material is of interest : Hg, 

 50-40; Au, trace; Ag, -12; Te, 49-48; total, 100-00. Specific 

 gravity, 9 21. 



The formula for coloradoite calculated from these figures is Hg, 

 Teg, requiring : Hg, 51*7 per cent.; Te 48-3 per cent. The pre- 

 viously accepted formula based upon analysis of small and impure 

 specimens was HgTe, requiring: Hg, 61-6 per cent.; Te, 38-4 

 per cent. — Geol. Sur. W. Australia, Bull. No. 6, p. 27. 



