J. S. Diller — Minercdogical Notes. 219 



ing can be predicted. If it exists it is certainly remarkable 

 that it should withstand the treatment with hydrofluoric acid 

 which the dumortierite received during the process of purifi- 

 cation. 



We are greatly indebted to Mrs. C. A. Bidwell for the sup- 

 ply of material for investigation, which at the cost of much 

 personal labor she so liberally furnished. 



U. S. G-eol Survey, Washington, D. C, Jan. 19, 1889. 



2. Supplementary note on the Periclotite of Elliott Co., Ky. y* by 



J. S. Diller. 



Dr. Geo. H. Williams recently identified perofskite in the 

 serpentine of Syracuse, 1ST. Y. (this Journal, vol. xxxiv, p. 140), 

 and suggested that the yellowish grains which were supposed 

 to be anatase in the peridotite of Elliott Co., Ky. (IT. S. Geol. 

 Surv. Bull. No. 38), may be the same mineral. To definitely 

 identify, if possible, the mineral in question the powdered 

 peridotitic rock was digested for a long time in HC1 until there 

 was nothing left with the yellowish mineral but a few grains 

 of garnet, enstatite and chromite. After careful washing, the 

 residue was subjected to the action of H 2 S0 4 raised slightly 

 above the temperature of the water bath. The yellowish 

 grains readily dissolved and an analysis by Mr. L. G-. Eakins 

 yielded the following results : 



Insoluble residue 50*79 



TiO„ 22-75 



FeO" 5-35 



CaO 10-28 



A1 2 3 1-48 



MgO 2-49 



Si0 2 6-13 



Total, 99-27 



The presence of A1 2 3 , MgO, Si0 2 and part of the FeO is 

 due to the fact that part of the garnet and enstatite were dis- 

 solved, for after the removal of the yellowish mineral they 

 were found to be slightly soluble under the conditions of the 

 experiment. The analysis clearly demonstrates that the yel- 

 lowish mineral is composed essentially of Ti0 2 and CaO, and 

 there is good reason to believe the mineral is perofskite as Dr. 

 Williams suggested. 



In the rock the ilmenite is f requently surrounded by a gran- 

 ular border of perofskite which may be so broad that the pe- 

 rofskite appears to completely replace the ilmenite as if derived 

 from it by alteration. Like the perofskite in the melilite 

 *This Journal, vol. xxxii, p. 121. 



