280 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



rough crystals up to 3 by 1 cm. in size. In powder under the micro- 

 scope this pyroxene is transparent and colorless, is biaxial positive 

 with 2V medium large; mean index, <3 = 1.6S0 and extinction Zac = 

 36°-39°. 



SHOSHONE COUNTY 



No pyroxene has been noted in the ores of the Coeur d'Alene 



district, but a pale green to colorless species, probably diopside, is 



abundant in some of the contact metamorphosed sediments near the 



monzonite intrusions. It has been noted particularly 



in the Alameda tunnel near the Granite (Success) 



/ 



TT 



/ / 

 i A 



: 



) mine, where some originally calcareous bands in the 

 / sediments have been changed to aggregates of diop- 

 / side, quartz, and green hornblende. 94 



SAHLITE 



LIME-MAGNESIA-IRON PYROXENE 



\ Calcium-iron-magnesium silicate inter- Mono-clinic, 



mediate between diopside and heden- 

 bergite 



In the absence of definite chemical or optical data it 

 is not possible to definitely place the position of a 

 pyroxene of this series and it is probable that some 

 of those described above as diopside are in reality 

 high enough in iron content to be designated by the 

 varietal name sahlite. 



BLAINE COUNTY 



A specimen from the Starlight mine in Elkhorn 

 Gulch near Ketchum in the Warm Springs district 

 consists of a green mineral in prisms up to 5 mm. 

 in length with interstitial calcite and considerable 

 coarse granular brilliant black sphalerite intergrown 

 with some pyrite. When the calcite is removed by 

 solution in dilute acid the green mineral remains 

 behind as lustrous prisms surrounded by spongy 

 masses of minute crystals of lighter green color. The 

 minute crystals are biaxial positive with 2V medium, 

 extinction 46°, refractive index /3 = 1.705 ±0.003. The larger prisms 

 are practically identical in optical properties with ,5=1.708, so that 

 the large and small crystals are both referable to sahlite. One of the 

 larger crystals was measured and found to be pyroxene of normal 

 habit. This crystal, which is illustrated in Figure 75, gave the 

 following measurements : 



}■ 



Fig. 75.— Sahlite. 

 Starlight mine, 

 Warm Springs 

 district, Blaine 

 County 



»• F. L. Ransome and F. C Calkins. U. S. Qeol. Survey, Prof. Paper 62, p. 99, 1908 



