354 



REPORT OF NATIONAL MUSEUM, 1899. 



Occurrence. The mineral occurs in granitic and feldspathic veins 

 in the form of crystals, crystalline granules, and cleavable masses. In 

 the United States it has been found in greater or less abundance in 

 nearly all the States bordering along the Appalachian Mountain sys- 

 tem (Specimen No. 63478, from Portland, Connecticut), in the Black 

 Hills of South Dakota, and also in California and Colorado. It has 

 also been found in Italy, Bavaria, Finland, Greenland, and western 

 South America. 



Uses. The material is used only in the preparation of salts of 

 columbium and tantalium, and as but a small quantity of these salts 

 are used, the mineral is in but little demand, except as mineralogical 

 specimens. 



2. YTTROTANTALITE. 



This name is given to a mineral closely related to samarskite (see 

 below), but carrying smaller percentages of uranium and lacking in 

 didymium and lanthanum. It is essentially a tantalate of yttrium 

 with small amounts of other of the rarer earths. (Specimen No. 60926, 

 U.S.N.M.) In appearance it is distinguished from samarskite only 

 with difficulty. Pyrochlore, fergusonite, aeschynite, euxenite, etc., 

 are closely related compounds, the commercial uses of which have not 

 yet been demonstrated. 



3. SAMARSKITE. 



Composition as given below. When crystallized, in the form of 

 rectangular prisms, but occurring more commonly massive and in 

 flattened granules. Cleavage, imperfect; fracture conchoidal; brittle. 

 Hardness, 5 to 6; specific gravity, 5.6 to 5.8. Luster, vitreous to 

 resinous. Color, velvet black. (Specimen No. 62772, U.S.N.M.) 



Localities and mode of occurrence. The only localities of importance 

 in the United States are the Wiseman Mica Mine and Grassy Creek 

 Mine, in Mitchell (Specimen No. 62772, U.S.N.M.) and in McDowell 



