W. P. Headden— Columbite and Tantalite. 



95 



only samples which are not unquestionably crystallized; it 

 may have been a very large crystal ; but it is not an aggregate 

 of crystals as was the mass from the Bob Ingersoll. 



I. 



II. 



6-181 



III. 



IV. 

 6-376 



V. 

 6-515 



Via. 



VI&. 



Vila. 



VII6. 



VIII. 



Sp. grav. 



5 890 



6-245 



6-612 







6-707 



6-750 



Cb 2 5 



54-09 



47-05 



46-59 



40-37 



39 94 



35-11 



35-17 



31-80 



31-31 



29-78 



Ta 2 5 



18-20 



34-04 



35-14 



41-14 



4296 



47-11 



47-08 



52-14 



52-49 



53-28 



Sn0 2 



•10 



0-30 



0-18 



0-13 



tr. 



035 



0-37 



o-io 



0-09 



0-13 



FeO 



11-21 



11-15 



7-44 



8-28 



8-59 



8-37 



8-38 



6-00 



6-10 



6-11 



MnO 



7-07 



7-80 



10-94 



9-09 



882 



9-26 



9-02 



10-7 



110-71 



10-40 



CaO 



•21 



100 88 



100-33 



100-29 



*0'88 

 99-89 



100-31 



10020 



100-02 



tr. 

 100-75 















100-70 



99-78 



Atom, equiv. 





















Cb 2 5 ) 



47-82 



3512 



34-80 



3012 



29-80 



26-16 



26-25 



23-73 



23-37 



22-22 



Ta 2 5 [ 



8-19 



15-33 



15-83 



18-53 



19-35 



21-62 



21-20 



23-48 



23-64 



24-00 



Sn0 2 ) 







0-21 



0-13 



0-09 





0-20 



0-20 



0-06 



006 



0-09 





56-01 



50-66 



50-76 



48-74 



49-15 



47-88 



47-65 



47-27 



47-07 



46-31 



FeO ) 

 MnO j" 



15-57 



15-48 



10-30 



11-50 



11-93 



11-62 



11-64 



8-33 



8-47 



8-48 



996 



10-96 



26-44 



15-40 



12-80 

 24-30 



12-33 



24-26 



13-20 



24-82 



12-70 

 24-34 



15-08 



15-08 

 23-55 



14-75 





25-53 



25-70 



23-41 



23-23 



Atom, ratios. 





















Cb : Ta = 



6: 1 



7:3 



7: 3 



5: 3 



3: 2 



5 



4 



1 



1 



1:1-08 



Fe: Mn = 



8: 5 



3 :2 



2 :3 



1 : 1 



1 : 1 



1 



1 



3 



5 



4:7 



* -10 MgO. 



XIY. Locality unknown. — This crystal was black, shining, 

 vertically striated, tabular in habit, with 010 somewhat curved 

 due apparently, to the successive deposition of thin plate-like 

 individuals, each a little narrower than the preceding one — 

 this cause will also explain the striation in this particular case. 



XY. Mallory Gulch. — digger Hill District. Material was 

 furnished me by Mr. Mark Hydliff, its color, streak and 

 powder were light-brown ; hardness inferior to that of the 

 columbite from the veins ; mass much cracked and inclosing 

 mica. Analysis X.Yb gives the result after treatment with 

 HC1. XYI. Same source, more compact but otherwise same 

 as preceding. 



Analyses XIY, XY, XYI, agree in giving the following 

 approximate molecular formula. 



3RCb 2 6 + 2RTa 2 6 , with H=Fe x Mn^ 



2 2 



These specimens have already undergone some alteration indi- 

 cated by the presence of lime, magnesia and ferric oxide solu- 

 ble in hot dilute hydrochloric acid. The low ratio of the 

 acids to the bases is probably due to this cause. A similar 



