418 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



The second sample of "typical hard ore" from the Waterloo 

 phosphate mine at Montpelier is a coal black dense rock with a 

 finely oolitic structure. In dilute hydrochloric acid it effervesces 

 giving off carbon dioxide, having a fetid bituminous odor, from the 

 matrix which dissolves first leaving the partly round and partly 

 subangular vitreous black phosphate granules in relief. Heated to 

 a red heat the matrix burns white while the granules remain black 

 accentuating the structure. Under the microscope the phosphate 

 is isotropic and varies from light brown to opaque black. The 

 index of refraction averages about 1.630. 



An interesting fact recently pointed out by G. R. Mansfield of 

 the United States Geological Survey is that the better grade phos- 

 phate rock carries vanadium in amount varying from 0.11 to 0.52 per 

 cent V 3 5 . 24 The phosphate deposits, all of which are about alike 

 occur in Bannock, Bear Lake, Bingham, Bonneville, and Madison 

 counties. 



PYROMORPHITE (550) 



Lead chlor-phosphate, 9Pb0.3P 2 5 .PbCl 2 . Hexagonal. 



Pyromorphite is a secondary lead mineral which is not common 

 in the western United States. It occurs sparingly in several mining 

 districts in Idaho and abundantly in places in a large number of 

 localities in the Coeur d'Alene district where very fine specimens, 

 have been obtained. 



BOISE COUNTY 



A specimen from Hall Brothers' property, Deadwood Basin, Dead- 

 wood district, contains tufts of minute acicular crystals of pale 

 yellow-green color and larger irregularly formed deep blue-green 

 prisms of pyromorphite. The pyromorphite is associated in the 

 specimen with cerusite. 



IDAHO COUNTY 



Specimens labeled "Vanadate of lead" from the Mallard Creek 

 prospect of W. Sendke, in the Dixie district, bear small green grains 

 and imperfect cr}*stals of pyromorphite on quartz which contains 

 galena and light yellow sphalerite. 



Another specimen, likewise labeled "Vanadate of lead" from 

 the Comstock mine, Dixie district, consists of cavernous rusty 

 quartz containing aggregates of minute yellow-green crystals. Ex- 

 amined under the microscope these are seen to be hexagonal prisms 

 with pyramidal terminations which are pleochroic in yellow-green 

 parallel to the elongation to colorless perpendicular to the elon- 

 gation. These contain no vanadium but react strongly for phos- 

 phoric acid and hence are doubtless pyromorphite. 



M G. R. Mansfield. U. S. Oeol. Survey, Mineral Resources of United States 1922, pt. 2, p. 116, 1923. 



