THE MINERALS OF IDAHO 



Measurmenls of sahlite, Figure 75 



281 



Quality, description 



Measured 



Very poor, dim 90 00 



Very good ' 90 00 



Good _ I 00 



Very poor, narrow ' 43 21 



Very poor, dim _J 90 00 



Medium i 35 43 



16 12 



90 00 



90 00 



90 00 



13 47 



54 40 



Calculated 



90 00 15 51 



90 00 , 90 00 



00 90 00 



43 33 ! 90 00 



90 00 

 35 36 



15 27 

 55 24 



A second specimen of similar material probably from the same or 

 an adjoining locality is also made up largely of pyroxene with calcite, 

 but contains more of the black granular sphalerite and a few brown 

 dodecahedral garnets. 



HEDENBERGITE 



LIME-IRON PYROXENE 



Calcium iron silicate, CaO.Fe0.2Si0 2 . Monoclinic. 



Only a few localities are known in the State for the iron end member 

 of the diopside series which seems to be decidedly rarer than the 

 magnesian diopside. 



ADAMS COUNTY 



Hedenbergite is listed by Livingston and Laney 95 with a question ( ?) 

 as occurring as a contact metamorphic mineral in the Seven Devils 

 district. 



CUSTER COUNTY 



Hedenbergite has been noted in the Alder Creek district as a 

 distinct mineral only in a few thin sections. Computation of analyses 

 of the pyroxene shows that it enters into the diopside in solid solu- 

 tion in amounts ranging from 9 to 23 per cent. 96 



A specimen from the Basin prospect shows abundant hedenbergite 

 as dull greenish to brown bladed fibrous masses mixed with galena. 

 This prospect is located on the mountain north of Park Creek, 

 which is the small stream occupying the low valley which connects 

 the upper valley of Trail Creek with the headwaters of Lost River 

 near where the Ketchum-Mackay road crosses the divide. Other 

 specimens from the same tunnel contain epidote, garnet, prehnite, 

 etc., in metamorphosed calcareous shale. Under the microscope the 

 hedenbergite is opaque except in thin splinters, from the presence 

 of an opaque brown pigment, probably limonitc, due to its easy 

 oxidation. Thin transparent splinters of the mineral appear color- 

 less with no pleochroism. It is biaxial positive with a mean re- 



's D. C Livingston and F. B. Laney. Idaho Bur. Mines and Oeol., Bull. 1, p. 62, 1920. 

 »« J. B. Umpleby. U. S. Geol. Survey, Prof. Paper 97, p. 53, 64, 1917. 



54347— 26t 19 



