J. S. Diller — Mioa-peridotite from Kentucky. 289 



uents, the designations adopted by him are as follows : — 

 picrite = olivine 4- augite, amphibole picrite = olivine -{-amphi- 

 bole, Wehrlite= olivine + dial lage, HarBburgite= olivine + rhom- 

 bic pyroxene, ZA6r3<?^fe=olivine-f-diallage+bronzite, dunite= 

 olivine-f-chromite without pyroxene or amphibole. 



Heretofore* no peridotitic rock has been recognized in which 

 biotitef has played the role of an original essential constituent. 

 While it is evident that the Flanary dike rock belongs to the 

 peridotites, it is clearly excluded from any of the subdivisions 

 above. In order that it may be conveniently distinguished 

 from other peridotites I propose for it the name mica-perido- 

 tite, a name which I believe will at once suggest to all students 

 of petrography its kinship. 



More than half a decade ago Prof. A. R. CrandallJ dis- 

 covered the peridotite of Elliott county, Kentucky, and to this 

 Mr. Ulrich now adds one more of the same type of rocks from 

 the western part of the State. Closely related rocks of the 

 same group have been described by Drs. J. C. Branner§ and 

 R. N. Brackett from Pike Co., Ark., by Prof. G. H. Wiliiams,| 

 from Syracuse, N. Y., and by Prof. J. F. Kemp,^[ from Ithaca, 

 N.Y. 



A very fresh olivine mica rock closely related to the mica 

 peridotite of Kentucky has been described by Dr. Max Koch,** 

 who recognizes it as a new type. It occurs in the gabbro region 

 of the Harz and contains augite and plagioclase as accessory 

 minerals in small quantities. These minerals as well as the 

 geologic relations of the rock indicate according to Dr. Koch, 

 that it belongs to the gabbro group. 



TJ. S. Geological Survey, Washington, D. C. 



* Excepting perhaps one described by Max Koch which will be noticed later. 



f The peridotitic rock described by Judd (Quart. Jour. Geol. Soc, Aug., 1885, p. 

 401), as scyehte is rich in mica; but he regards it as secondary resulting from the 

 alteration of augite. Furthermore, scyelite contains hornblende of which not a 

 trace has been found in the rock from Flanary dike. 



% Geol. Survey of Ky., Report on the Geology of Elliott County, by A. R. Cran- 

 dall, p. 17. See also articles by J. S. Diller, this Journal, Aug. 1886, and U. S. 

 Geol. Survey, Bulletin No. 38. 



§ This Journal, vol. xxxviii, p. 50, 1889; also, Geol. Survey of Ark. Annual 

 Rept. for 1890, vol. ii, p. 377. 



|| Ibid., vol. xxxiv, pp. 140-142, 1887. 



•IT Ibid., vol. xlii, p. 410, 1891. 



**Zeitschr. d. d. geolog. Gesell., xli, p. 163, 1889. 



