THE MINERALS OF IDAHO 453 



The mineral is partially soluble in concentrated hydrochloric acid 

 with evolution of carbon dioxide. There is no doubt as to its identity 

 as leadhillite. 



CALEDONITE (739) 



Basic sulphate of lead and copper, Orthorhombic. 



4Pb0.2Cu0.3S0 3 .3H 2 0. 



Caledonite probably occurs in a number of places in the State, 

 and has been tentatively identified on specimens from several locali- 

 ties. In all of these the material thought to be caledonite is present 

 in small amount and the identification was in no case positively 

 established. 



CUSTER COUNTY 



Caledonite was doubtfully identified as a minutely crystalline 

 crust on malachite in oxidizing galena-tetrahedrite ore from the 

 Hoosier mine in the Bay Horse district. 



FREMONT COUNTY 



Some very minute blue-green crystals, entirely too small for 

 measurement, occurring with linarite in a specimen from the Wilbur 

 mine in the Dome district are probably caledonite. 



OWYHEE COUNTY 



A specimen of oxidized lead ore from the Laxley mine, South 

 Mountain district (Cat. No. 5459 U.S.N.M.) contains a pale green 

 mineral which is probably caledonite associated with linarite and 

 cerusite. The caledonite forms minute waxy globules, a part of 

 which have a crystalline surface like the globules obtained by fusing 

 pyromorphite. 



SHOSHONE COUNTY 



Thin pale green coatings which are not carbonate and are probably 

 caledonite occur in small amount with linarite and leadhillite on a 

 specimen from the Caledonia mine. Blue-green friable masses of 

 microscopic crystals occur intermixed with linarite which coats 

 galena in a specimen from the Lookout Mountain mine on Pine 

 Creek. The material is in amount too small and is too mixed with 

 linarite and cerusite to permit material to be isolated for chemical 

 testing. Under the microscope these minute crystals are tabular 

 rectangles with truncated corners. These give parallel extinction 

 with the obtuse bisectix perpendicular to the flat side and negative 

 elongation. They are biaxial negative then with 2V large. Assum- 

 ing the optical orientation given for caledonite by Larsen they are 

 tabular to c(001) and elongated on the b axis while the corners are 

 truncated by faces of ra(110). Measurement under the microscope 

 of the angle between two of these truncating faces gave 84° which 

 compares well with the angle of the prism, 85° 0', of caledonite. 



