274 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



shown in Figure 74, which showed also narrow line faces of (010) 

 from the Blaine tunnel gave the following measurements: 



Measurements of valencianite 



MICROCLINE (315) 



Potassium aluminium silicate, Triclinic. 



K 2 O.Al 2 3 .6Si0 2 . 



The triclinic potash feldspar,, microcline, is probably of frequent 

 occurrence as a constituent of granitic igneous rocks in Idaho. Only 

 the following occurrence has been especially mentioned. 



SHOSHONE COUNTY 



On Ninemile Creek, above the forks, where the railroad to the 

 Success mine swings around the point of the hill and numerous cut- 

 tings are made in the southern syenite border of the Coeur d'Alene 

 batholith, a part of the rock is strikingly porphyritic with numerous 

 phenocrysts of feldspar in a matrix apparently consisting in the main 

 of parallel needles of hornblende. The feldspar crystals are uni- 

 formly about an inch in length, are cream white to pinkish in color 

 and many of them show carlsbad twinning. This feldspar has been 

 found by F. C. Calkins to be microcline. 86 



ALBITE (316) 



SODA FELDSPAR 



Aluminium-sodium silicate, Triclinic. 



::u 2 O.Al 2 3 .6Si0 2 . 



I ike the other feldspars albite is probably much more widespread 

 in c ccurrence in the state than existing records might seem to indicate. 

 Oniy a single specific occurrence of mineralogic interest has been 

 reported. 



ADAMS COUNTY 



At the Helena claim in the Seven Devils district intrusive granodio- 

 rite near its contact with limestone is rather intensely altered with the 

 development of much zoisite. It has also suffered considerable 

 sericitization and in many places contains open vugs or spaces lined 

 with drusy well terminated colorless albite crystals. 87 It has not 



8« F. L. Ransome and F. C. Calkins. U. S. Oeol. Survey, Prof. Paper 62, p. 49, 1908. 



« D. C. Livingston and F. B. Laney. Idaho Bur. Mines and Geol., Bull. 1, pp. 64, 75-76, 1920. 



