c ll \i;\( I ! KISTICS OF THE ORE. 15 



The mineral scorns to be dose t<> liamlinitc, for which the formula, 

 as recalculated byTrior^ is 2SiO.3AI 2 Q 8 .2P.,(),.7lI_.O, but as a little 

 sulphur is present it probably belongs in the scries between hamlinito 

 and svanbergite (2SrO.3Al 2 O 3 .P 2 O 5 -2SO 3 .6H 2 O). Another mineral 

 of the same group, hinsdalite (2PbO.3Al 2 O 3 -P 2 O 5 .2SO 3 .6H 2 O), was 

 discovered in 1010 by Larsen 2 as a vein mineral in the Golden Fleece 

 mine, near Lake City, Colo. 



The same mineral has been found in sections from other parts of the 

 Boulder field, though not in such large quantity as in the Eagle Rock 

 specimen. Sections of ' 'horns tone " ore from other places have shown 

 none of it. However, phosphorus in small quantity is nearly if not 

 quite a universal component of the Boulder County tungsten ores. 



Hugh F. Watts, who lias assayed thousands of samples of ferberite 

 ores and concentrates coming from ah 1 parts of the Boulder field, 

 states that whenever he has tested for it he has found phosphorus 

 present. 3 In one test on a composite of seven ores the phosphorus 

 present amounted to 0.038 per cent. Hills 4 notes from 0.01 to 0.02 

 per cent phosphorus in eight out of nine analyses of concentrates 

 and a trace in the other. Greenawalt 5 notes 0.05 per cent in a 

 concentrate from Gordon Gulch. No apatite or other phosphate 

 except the hamlinite (?) has been found, and it seems reasonable 

 to suppose a very wide distribution of the hamlinite (?). The min- 

 eral apparently occurs only in the quartz gangue, and if the ore 

 is finely ground before separation very little will be left in the con- 

 centrates, for its specific gravity (more than 2.8 and probably not 

 higher than 3) is so low that it would readily pass into the tailings. 



I hope to make further investigation of this mineral. 



Hematite (specular). At the south end of the Black Hawk No. 1 

 vein, 1^ HHRff^oTrfBToTNederland, a short vein which is nowhere more 

 than a few inches thick, the ferberfie gives way to specular hematite. 

 This mineral is also found in small quantity in some other veins, and 

 what is known as the May vein, a short distance east of the Black 

 Hawk No. 1 vein, is a series of anastomosing veinlets made up of spec- 

 ular hematite, which is said to be accompanied by a little tungsten, 

 though none could be found in specimens collected. Hills 4 gives 

 an analysis of ferberite concentrates from "the east side of the dis- 

 trict," in which the content of FeO exceeds that of WO 3 , and another 

 in which the quantity of FeO is only a little less than that of WO 3 . 

 i'he analyses follow. 



1 Prior, G. T., Hamlinite, plumbogummite (hitchcockite), beudantite, and svanbergite, as members of 

 a natural group of minerals: Mineralog. Mag., vol. 12, p. 253, 1900. 



* Larsen, E. S., and Schaller, W. T., Hinsdalite, a new mineral: Am. Jour. Sci., 4th ser., vol. 32, p. 251, 

 1911. 



* Private communication. 



4 Hills, V. G., Tungsten mining and milling: Colorado Sci. Soc. Proc., vol. 9, p. 149, 1909. 



* Greenawalt, W. E., The tungsten deposits of Boulder County, Colo.: Eng. and Min. Jour., vol. 83, p. 951, 



1907. . 



