Hidden and Warren — Yttrocrasite. 515 



Art. XLIV. — On Yttrocrasite, a New Yttrium- Thorium- 

 Uranium Titanate ; by W. E. Hidden and C. H. Warren. 



The crystal, from which the material for analysis was selected, 

 was found about three years ago in Burnet County, Texas, by 

 Mr. John J. Barringer, who discovered the famous gadolinite 

 mine just across the Colorado River in Llano County, now 

 known as Barringer Hill. The crystal was found among the 

 debris thrown out from a small prospect pit, dug for gadolinite. 

 and was the largest of several pieces observed in the loose peg- 

 matite material. The locality is east of and nearly opposite 

 Barringer Hill and distant from it about three miles. It is sit- 

 uated in Burnet County and in a region where coarse granite 

 and pegmatite abound. This crystal when first found weighed 

 about sixty grams, and was complete except at one end. It, 

 showed orthorhombic symmetry, but the faces were not smooth 

 enough for satisfactory measuring. The type of form closely 

 resembled the figure of yttrotantalite, on page 738 of Dana's 

 System of Mineralogy. The three pinacoids, the unit prism, 

 and one orthodome were apparent. The basal plane predomi- 

 nated. 



The crystal had a thin dull brown coating of amorphous mate- 

 rial which was evidently an hydrated alteration product, very 

 similar to the yellowish brown coating observed on the poly- 

 crase (?) of North and South Carolina. The fresh underlying 

 material is black in appearance, and has a bright pitchy to 

 resinous luster, and closely resembles that of poly erase and 

 euxenite, and like these has an uneven and small conchoidal 

 fracture. Its hardness is between 5*5 and 6. 



Under the microscope fragments of the mineral show, 

 through their edges, a rich amber to light yellow color. Ex- 

 tremely thin pieces are almost colorless and transparent. 

 In some portions near the surface minute black specks, sug- 

 gestive of alteration products, or mechanical inclusions, were 

 observed scattered through the material. The mineral when 

 examined between crossed nicols is seen to consist of a mixture 

 of isotropic and a feebly double refracting material. In sev- 

 eral instances a distinctly spherulitic structure was observed with 

 high powers, otherwise nothing of a definite nature could be 

 made out regarding the optically active portion. The mineral 

 is not now, therefore, of a strictly homogeneous structure. This 

 fact taken into consideration with its content of water and car- 

 bon dioxide suggests that the mineral is a hydrated alteration of 

 an originally anhydrous species. It may be mentioned here 

 that a very similar heterogeneous structure has been also 

 noticed as • characteristic of specimens of polycrase (?) from 

 North and South Carolina. 



