

1889.] NATURAL SCIENCES OF PHILADELPHIA. 51 



Scarcity of material prevented a direct determination of the fer- 

 rous oxide which was calculated from the amount of ferric oxide 

 found. 



Columbite. 



At Mineral Hill, Middletown Twp., Delaware County, Pa., as a 

 great rarity, a few specimens of columbite have been found ; amongst 

 which were two crystals, the larger and better in the W. S. 

 Vaux Collection of the Academy of Natural Sciences, the smaller 

 in the cabinet of Mr. Clarence S. Bement, who kindly loaned it for 

 a crystallographic determination, which was made at the suggestion of 

 Dr. Edward S. Dana by Mr. H. S. Washington, who very kindly 

 made the following measurements of such angles as were worth re- 

 cording, and prepared the accompanying drawing. For comparison, 

 Dr. Dana gave the angles of the Standish columbite : 



Mineral Hill. 



100 A HO = 40° 1' 



010 A 130 = 21° 49' 



100 A 233 = 63° 41' 



233 A 133 = 12° 4' 



001 A 133 = 42° 57' 



Besides these two crystals, two or three 



crystalline masses were found, one of which 



has been presented to me for investigation 



by Mr. Thos. S. Ash. 



It weighed a little over 30 grams, was 



28 mm long, by 20 and 18 mm , tapering at both 



ends. A small quantity of black mica was 

 associated with it. The exterior had a brownish-black to a reddish- 

 brown color, a subconchoidal fracture and a submetallic luster, in- 

 clining to resinous ; the interior of the lump was more compact, 

 with an uneven fracture, iron-black color and very little luster. 



With great care the blackest and less lustrous, which formed the 

 greater portion of the specimen, was selected for analysis. Fracture 

 uneven, no sign of cleavage. The spec. grav. was found in two dif- 

 ferent portions=5.262 and 5.259, which is, I believe, the low T est 

 specific gravity ever observed for any columbite. 



The analyses were made in the usual way ; an approximate sepa- 

 ration of Ta 2 O 5 from Cb 2 O 5 was obtained by Marignac's method. 



Standish. 

 39° 38|' 

 21° 55' 



61° 52' 

 Not very 13° 10' 

 good. 43° 48' 



