Hidden and Pratt — Associated Minerals of Rhodolite. 467 



panning them down to a practical minimum. This sample 

 weighed 1*75 grams and represented the gold from many hun- 

 dred cubic yards of gravel and thus proved its rarity in this 

 locality. 



This gold was assayed and the resulting button weighed 

 1*2757 grams. Its specific gravity was 17*88. The pure gold 

 weighed after separation from the alloyed silver 1*1583 grams, 

 showing the Mason's Branch gold to be 90*77 per cent " fine." 

 This is interesting because the neighboring Caler Fork (distant 

 two miles !N". E.) gold* had a " fineness " of 90*10 per cent and 

 thus a constancy is shown for the region generally. In the 

 concentrates containing this gold, over 300 crystals of sperry- 

 lite were found and also all the other characteristic minerals 

 mentioned by one of us as occurring with sperrylite from 

 Caler Fork.* 



Sperrylite. — The most important mineral found associated 

 with the rhodolite is sperrylite. It was first found among the 

 gold particles in a similar manner to that discovered by one of 

 us on Caler Fork, in Macon County.* 



From the If grams of impure gold already mentioned, about 

 300 crystals of sperrylite were finally separated by using a 

 strong pocket lens and a moistened needle point. The gold 

 sands were spread out upon glass to avoid their jumping when 

 touched, as the particles are prone to do from paper or wood. 

 The crystals have sharper edges and are somewhat larger and 

 brighter than those from Caler Fork. The entire "find" 

 did not exceed one milligram in weight and the largest crystal 

 was 0*4 mm in diameter. The octahedron 

 apparently predominates, though many 

 of the crystals show an equal develop- 

 ment of the cube and octahedron. On 

 a very few of the crystals, there was a 

 slight development of the pentagonal 

 dodecahedron <?, 210, represented by fig. 

 2, which was prepared by G. H. Edwards 

 of the Sheffield Scientific School, who 

 identified the faces by the following 

 measurements : 



Measured. Calculated. 



O^a, 111^010 54° 56' 54° 44' 



• A 0, 111/^111 70 48 70 32 



a A e, 100^210 26 28 26 34 



These results prove that these sperrylite crystals are iso- 

 metric and pyritohedral and, therefore, are like the original 

 sperrylite from the Algoma district, near Sudbury, Canada. 



* This Journal, vol. vi, p. 381, 1898. 



