114 schaller: barbierite 



MINERALOGY. — Note on barbierite, monoclinic soda feldspar. 

 Waldemar T. Schaller To appear in a bulletin, "Miner- 

 alogical notes, Series II " of the U. S. Geological Survey. 



In a recent paper 1 1 proposed the name barbierite for the mono- 

 clinic soda feldspar isomorphous with orthoclase. A feldspar 

 from Kragero, Norway, analyzed by Barbier and Prost 2 - is nearly 

 pure barbierite, as only 1.15 per cent K 2 was found. 



Professor Barbier was kind enough to send me some slides of 

 the feldspar from Kragero which, according to his analysis, 

 consists essentially of the soda compound. One of the slides, a 

 basal section giving parallel extinction and appearing uniform, 

 was uncovered and the feldspar washed free from Canada balsam. 

 The mineral was then immersed in an oil with refractive index 

 of 1.530 and it was seen that the index of the mineral was con- 

 siderably lower than that of the oil. If the orientation of the 

 mineral is the same as that of orthoclase then a basal section would 

 yield values for a and for y. As these were both found to be de- 

 cidedly lower than 1.530, the section cannot be albite 3 . Unfor- 

 tunately the very small section was accidentally lost before its 

 soda content could be verified microchemically. The existence 

 of a monoclinic form of the compound Al 2 3 .Na 2 0.6Si02, differ- 

 ent from albite, is therefore established. 



PETROLOGY. — Note on some albitite dikes in Nevada. Fred- 

 erick Leslie Ransome, Geological Survey. 



The dikes here described occur in the southeast corner of Hum- 

 boldt County, about thirty miles east-southeast of Lovelock, in 

 that part of the Pahute Range that is locally known as the Still- 

 water, Silver, or Table Mountain, Range. They are associated 

 with the nickel deposits of Cottonwood Canyon 1 and are intrusive 

 as rather short irregular bodies into andesite and diorite. 



'Amer. Jour. Sci., 4th ser., 30: 358. 1910. 



2 Bull. Soc. China., Ill, p. 894. 1908. 



3 For albite, a = 1.529, y= 1.539. 



' Ransome, F. L.: Notes on some mining districts in Humboldt County, 

 Nevada. Bull. U. S. Geol. Survey No. 414, pp. 55-58. 1909. 



