236 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



being subordinate in amount. Where found it is considered an 

 indication of good ore. The carbonate is fine-grained and somewhat 

 crushed and friable. It has a pale pink color which is only conspic- 

 uous when the mineral is moist. Upon analysis a selected and pure 

 sample gave the following results, stated as carbonates of the respec- 

 tive bases. 



Analysis of rhodochrosite, Conjecture mine 



(E. V. Shannon, analyst) 



Constituent Per cent 



Manganese carbonate (MnC0 3 ) 60. 26 



Iron carbonate (FeC0 3 ) ,- 12. 86 



Calcium carbonate (CaC0 3 ) 11. 06 



Magnesium carbonate (MgC0 3 ) 15. 48 



Total 99. 66 



Since manganese carbonate is clearly predominant this mineral is 

 called rhodochrosite. 



LEMHI COUNTY 



Rhodochrosite is reported to occur in minute crystals on fracture 

 surfaces in ores of the Kittie Burton mine in the Indian Creek district 

 associated with malachite, azurite, and earthy oxides or iron and 

 manganese. 51 Beautiful specimens of this carbonate have also been 

 reported from the Blackbird district. 52 



SMITHSONITE (275) 



DRY BONE 



Zinc carbonate, ZnC0 3 . Rhombohedral. 



Smithsonite, the zinc carbonate, usually known to miners under 

 the name " dry bone, " is often an inconspicuous earthy appearing 

 mineral which is easily overlooked and may occur in the oxidized 

 portions of many veins which contain primary zinc sulphides. It 

 has been identified at a few localities in Idaho as given below. 



BLAINE COUNTYj 



Smithsonite is common in the surface ores of several mines in 

 Blaine County. The Kusa Mining Co. shipped several carloads of 

 high-grade zinc carbonate ore in 1918 from claims on Boulder Creek 

 in the Wood River Region. 53 Small botryoidal crusts of gray to 

 pale green smithsonite occur in prospects high on the mountain 

 south of Trail Creek near Ketchum. In the Era district smithsonite 

 occurs with cerusite and silver minerals in the Ella mine near the 

 head of Ella Canyon. 54 



81 J. B. Umpleby. U. S. Geol. Survey, Bull. 528, p. 138, 1913. 



i! J. B. Umpleby. Idem, p. 78, 1913. 



« Robert N. Bell. Mining Industry of Idaho. Rept. State Mine Inspector for 1918, p. 63. 



54 J. B. Umpleby. U. S. Oeol. Survey, Prof. Paper 97, p. 121, 1917. 



