436 



PROCEEDINGS OF THE ACADEMY OF 



[1897. 



The Umen mountains which lie close to the town of Miass are 

 celebrated as the depository of many, both intrinsically and scien- 

 tifically valuable minerals, some of which are peculiar to the 

 range. Thus, Miaskite (nephelinic or eloeolitic syenite with Biotite), 

 named by Gustav Rose, is not peculiar to these mountains only, 

 which bear the name of Ilmen, but also to their prolongations and 

 the mountains Baiksky, Sobatchia, Potanina and Wichniowaia. In 

 this continuation another characteristic rock is found composed of 

 Anorthite and Corundum. In the gneiss of the Ilmens and their 

 northerly prolongations veins of a rock composed essentially of 

 corundum and orthose are found. M. Karpinsky considers this an 

 analogue of the syenites, the corundum taking the place of the 

 biotite. 



The Ilmens are thus more uniform and characteristic throughout 

 the 150 kilom. of their length than the main chain of the (Jural 

 itself. " Miascite" (or Miasskite, or better Miassite or Biotite- 

 nepheline Syenite) is found in many places in the Ilmens, of which 

 the chief is near Lake Ilmen. There and in most of the other 

 localities are developed the granular and gneissic varieties of 

 Miassite, cut by veins of very coarse-grained Miassite. A foot note 

 in L. G. V., 22, gives the following as yet unpublished analysis of 

 Miassite by M. Bourdakow : 



Si0 2 



TiO, 



A1 2 3 



Fe,0 3 



FeO 



MnO 



CaO 



MgO 



Na 2 



K 2 6 



C0 2 



H,6 



I. Granular Miassite near 

 Lake Ilmen. 



III. Schistose Miassite from 

 Mt. Sobatchia. 



II. Schistose Miassite from 

 Mt. Wichniowaia. 



There are over 150 mineral localities exploited in the Ilmen 

 mountains in the neighborhood of Lake Ilmen. The minerals (of 

 which a list of 83 is given in L. G. V. by Karpinsky, and 35 are 



