1892.] Mineralogy and Petrography. 



stone gave rise to perofskite, magnetite, apatite, phlogo] 

 ite and rnonticellite. 



In the potash Sulphur Springs region the eleolite and 

 are but little different from those of Magnet Cove. The 

 tact with one of the eleolite-syenite dykes, however, dil 

 from the contact rocks of other regions. Close to the 

 shale has a glassy appearance, and is cut by sheets and r 

 and white minerals and bands of coarse crystalline ealci 

 microscope sections are seen to consist of plagioclate, wo 



wolla>tonite), in which a tenth of the Cat) has been ivplae.-d ■■} V. < > 

 The author calls the variety natroxontolite. 



Outside of the regions above mentioned aegirite-tinguite dykes«,rcur 

 at Hot Springs and at Hominy Hill, in Sec. 27, T. 1 X. K. 14 W . 



The basic dykes outside of the syenite areas have Wen studied by 

 Kemp, whose report comprises the twelfth chapter of the book under 

 review. Most of them are narrow. In composition they are s. > closely 

 related to the rocks already mentioned in this abstract that thes are 

 regarded as genetically connected with them. The most interest, n- ot 

 the dyke masses are the ouachitites. These are dark in color, and are 

 all porphvritic, with very large phenocrysts of biotite and augite. The 

 groundmass in which these are imbedded is composed of augite, mag- 

 netite and glass. An analysis of one of these rocks yielded : 



Si0 2 TiO A1A FeA FeO CaO MgO K 2 Na 2 H 2 C0 2 P 2 5 Tot. 



vuAn ao i,>a. qot iso u.ifi 11.44 :i.i.H -S*T -^ 3.!»4 1.04=99.84 



This rock, which is so very basic, is a constant associate of the more 

 acid eleolite-syenite. All the basic dykes that have thus far been dis- 

 covered in the State are mentioned in a table containing 280 entries. 



In conclusion the author recapitulates his classification as tallow.: 

 The eleolite plutonic rocks are called eleolite-syenites. From these are 

 sharply separated the dyke forms, mentioned under eleolite- syenite 

 dyke rocks, which are not porphvritic, but in the variety pulaskite 

 (hornblende eleolite-syenite) are trachytic; the eleolite porphyries, in 

 which eleolite phenocrysts occur; and -the tinguites, characterized 

 by porphyria crystals of orthoclaae. Among the latter are the eleo- 

 lite, leucite and aegi rite varieties. 



