168 The American XaturalUt. [Februar 



cutting the crystalline schists and granites- of the Western part of th 

 Argentine Republic have been carefully examined by Sabensiji 

 They are aggregates of orthoclase, microline, quartz and mica, wit 

 plagioclase, biotite, chbrite, tonrnialine, garnet, bervl, apatite, zireo: 

 and hematite as accessory components. Both the potassium feldsptl 

 are intergrown with albite lamella;, inlaid parallel to a plane betweei 

 oo P^- and 2P-^. The microline offered a fine opportunity for th 

 study of its characteristics. An untwinned specimen gave as a meai 

 of the measurements of its cleavage faces the angles 89° 30.6' am 

 90° 29.4'. The peculiar grid-iron structure seen in certain thin sec 

 tions of the minerals are ascribed to twinning according to the albit 



pericline laws. The arguments brought forwa 



rd in support of this 



view are too involved to be dealt with in this pi; 





stated in the author's article. Gas and fluid incl 



usions were formed in 



the quartz, which mineral often i 



unduloua extinction. 



Quartz and feldspar are frpfjiient.lv inter-row n 



to give rise to the 



graphic structure. This is explained l.v the nut 



hor as a regular inter- 



growth of the two minerals j„ a manner analog 



oufl to that of ortho- 



clase and albite, /. c, the quartz follows easv el 



eavaee planes in the 



feldspar. 





Mineralogical News.— Of some rare Aigen 



,,ine minerals recently 



described by Klockmann" the following de^ei 



•ve notice: E»hmte, 



Umangite and Lvznnih. The first namc.fis rega 



irded by the author as 



a member of the galena group, in spite of the fa 



ct that it appears to 



possess a foliated structure and an hexa-ona! 





yielded: Ag = 43.13; Cu . 2">.:Ji' : Se :;i. 



55 corresponding to 



Ag, Cu, Se, or a jolpaite in which Se replaces S. 



The mineral occurs 



in a vein with calcite and umangite, cutting a li 





age. The umangite has heretofore been mista 



ken for harite. An 



analysis of the purest material obtainable 



gave: Co9»(M| 



Ag = 49; 8e = 41.44; Co,, H.O, etc., 2.04 





impurities irives a result corresponding to ( 'u Se 



Its density is 5.620. 



The mineral, which is new, is found massive and 



in the form of • very 



full-grained granular aggregate It- hardness is 



3. It ha- a metallic 



lustre and is opaque. ItTstrvak U hhek while it- 



color in consequence 



of corrosion is a dark, cherrv red or violet. The 





the locality iu which it occur- -on the We-t s 



lope" of the Sierra de 



"XcuesJahrb.furAlnr. 





"Zeils.f. Kry f, ., |,s . 





