Mangano-Columbite and Microlite in Maine. 461 



made on columbite from Standish, Me., having a specific grav- 

 ity of 5*65, and which according to the analysis of Allen* con- 

 tains only a little tantalum and manganese. 



Several forms gave rather unsatisfactory reflections. Some 

 of the measured and calculated angles are as follows : 















Calculated for 







Calculated. 



Measured. 



Columbite. 



/w/', 



102^102 = 



55° 



40' 



55° 



40'* 



56° 



28' 



Jc ^ kf, n 



103^103 = 



38 



47 



38 



52 



39 



23 



d /\ d , 



730^730 = 



39 



25- 



39 



56 



39 



6 



m/^m'", 



110/vllO = 



79 



47 



79 



47* 



79 



17 



9*9'", 



130*130 = 



136 



31 



136 



51 



136 



10 



9*9', 



130*130 = 



43 



29 



44 



5 



43 



50 



e /s e\ 



021*021 = 



120 



57 







121 



20 



m ^ o, 



110*111 = 



36 



oi 



35 



55 



35 



38 



o ^ o\ 



111*111 = 



76 



44 







77 



29 



O S^O'", 



111*111 = 



62 



30$ 







62 



27^ 



7T A^'j 



121*121 = 



55 







55 



3 



55 



30 



7t a. 7t , 



121*121 = 



101 



2 







100 



59 



n /s n\ 



]63 A 163 = 



19 



42 







19 



54 



n ^ n'", 



163*163 = 



118 











118 



20 



u s\ u'", 



133*133 = 



79 



32 











One variation from columbite shown by the habit of these 

 crystals is that the form/*, which is the predominating one at 

 the termination of all of the crystals, is of rare occurrence and 

 has previously been observed only with slight development on 

 columbite. 



Microlite. 



Yery beautiful crystals of microlite averaging 2 mm in diam- 

 eter of a honey-yellow color and high luster are found spar- 

 ingly at the locality. The prevailing form is the octahedron, 

 modified by the dodecahedron and sometimes by the icositetra- 

 hedron, 113. The habit is then very much like that of the 

 pyrochlore figured on page 762 of the sixth edition of Dana's 

 Mineralogy. The specific gravity, taken by Professor Penfield 

 on 0*2642 gr. of material was found to be 5*17, which is some- 

 what low for microlite and due probably to the presence of a 

 little more niobium than usual. A qualitative analysis indi- 

 cated the presence of calcium and of tantalum in considerable 

 excess over niobium. 



In closing, I wish to express my thanks to Professor Penfield 

 for his kind assistance during the entire investigation and to 

 Mr. Bailey for a generous supply of the rare and interesting 

 minerals from this locality. 



Laboratory of Mineralogy and Petrography, 

 Sheffield Scientific School, New Haven, November, 1895. 



*Zeitschr. Kryst, xii, p. 272, 1886. 



