286 J. S. Diller — Mica-peridotite from Kentucky. 



Art. XXXYII. — Mica-peridotite from. Kentucky; by J. S. 



Diller. 



In November, 1890, I received from Mr. E. O. Ulricli of 

 the Geological Survey of Kentucky the information that a dike, 

 called the Flanary dike, had been discovered in Crittenden 

 Count} 7 of that State. The specimens from the dike sent to me 

 at that time for examination were laid aside awaiting the report 

 upon the eruptive rocks of Arkansas by J. Francis Williams, 

 and J. F. Kemp. It was expected that similar rocks would be 

 found in Arkansas and this paper rendered unnecessary. 



Mr. Ulrich has kindly furnished me the following informa- 

 tion concerning the occurrence of the rock in the field. 



The dike is in a fault striking N. 44 E. Although the peri- 

 dotite has not yet been found all along the fault it is known to 

 occur at four points on the line with a distance of 6 miles 

 between the extremes. In Livingston county a little was seen 

 in a shaft mixed with fluor spar and other vein matter. A 

 mile and a half northeast of the county line and three miles 

 from the locality just noted, a shallow opening exposes consider- 

 able decomposed peridotite of a light gray or ash color. Here 

 again it is associated with vein matter chiefly fluor spar. At 

 the Flanary shaft the dike is over 20 feet wide with no wall 

 seen on either side. Crosscuts were made 6 feet on one side 

 and 8 feet on the other without finding the walls. It may be 

 that the shaft is at the intersection of several veins in a sort of 

 " chimney." A quarter mile southeast on the Holly the vein 

 matter is 6 feet solid and pure fluor spar. The dike break 

 separates strata faulted no less than 800 feet with the St. Louis 

 beds on the northwest and the upper Chester and coal-measure 

 conglomerate on the southeast. 



At least one other dike has been discovered in the county 

 and Mr. Ulrich thinks its material is closety related to that of 

 the Flanary dike. It occurs in a much tumbled region just 

 south of the Columbia mines which he regards as the chief 

 center of disturbance. 



The specimens for my study were selected by Mr. Ulrich 

 from among the material thrown out of the Flanary shaft. 

 The shaft is 45 feet deep and the material exposed to surface 

 weathering for nearly two years. The rock is dull greenish- 

 gray. At first glance it has a granitic aspect but upon closer 

 examination the resemblance disappears. It contains many 

 small dark greenish spots besides brownish scales of mica. 

 Upon comparing it with an altered specimen of the peridotite 

 from Elliott county, Ky., one is led at once to suspect that 



