‘crystals of this mineral in such a manner as to bring out the 
1112 General Notes. uf Dec 
singly. The most notable fact in their consideration is the sup- 
osed occurrence of topaz in the felsite and the grouping of little ` 
me 
E E ac a a a cca E 
inclined to regard . . . as probably being more or less altered 
volcanic tuffs, or as sedimentary rocks mainly composed of erup- 
tive material derived from the disintegration of rocks of a dioritic 
small for isolation. In an aplitic tourmaline gra 
Zschillen, near Wechselburg, in Saxony, Cohen fi 
ficient quantity for isolation, but not for analysis. ‘ 
occurs in isolated columnar and acicular forms, and not in S 
as in the case of contact rocks and the crystalline schists. 
Mineralogical News.—A fter experimenti 
high temperatures on the optical properties of faujasite cry 
Rinne? concludes that this mineral is normally regular 
tallization. When exposed to the air it begins to lo 
becomes uniaxial, breaking up at the same time into eig 
dinary ray becomes less and less as the temperature Z 
until at 150° =e, At this temperature the mineral 
* Comptes Rendus, cv., 1887, pe 247+ 
zi Neues Jahrb. f. Min., etc., 1887, ii. p- 178. 
