620 



HENRY S. WASHINGTON 



approximately that of Williams' specimen. It is probable that 

 my specimen was rather richer in nephelite and poorer in dark 

 minerals than Williams'. The composition is much the same 

 in a general way as that of the ijolite, only that it is melano- 

 cratic, rather than mesocratic. 



Jacupirangite. — A new analysis was made of the dark, coarse- 

 grained rock, composed largely of augite, which occurs as a 

 small mass northeast of the main area, on Cove Creek. This 

 was deemed to be advisable since the analysis of Williams 

 showed more CaO, or less MgO and FeO, than was necessary 

 to form augite or any other mineral present. The analysis of 

 Williams is given in I, and my results in II, with two other 

 analyses for comparison. 



No. 



SiOg 



AI2O3 



FegOg 



FeO 



MgO 



CaO 



NagO 



K3O 



H3O IIO° + 



HgO 110° — , 



COg 



TiOg 



ZrOg 



X 



P2O5 



CI 



s 



MriO 



BaO 



SrO 



36.51 ' ;> 



8.22; ; 

 8.29,,.i 



8.iq-.. 



18.85 j;,( 

 2.10 i_-~ 



i.oSV' 

 1 .40 



3-II,::" 



0.03^ 

 " / trace 

 trace 



99.22 



38.39 

 7-05< 

 9-07,^ 

 6.17 . 



11.58; 



19.01 , 

 0.74 

 0.75 

 0-33 

 0. 14 

 0.32,, 



4-54. 

 none 

 0.24 

 0.82 



. 42 ; 

 0.32 



trace 



of- 



99.89 



III 



6.15,- 



II .70 c 7 

 8.14.-/- 



ii.47'r.? 

 18.60 c;.^. 



0.78' J 



0.13 00, 



0-54 



0.18 



none 



4 . 32 ,. 



0. 17 



0. 16 



100.72 



IV 



15 



Sp. gr., 3.407 — 26° C. ' . ° - ' 



I. Jacupirangite, Magnet Cove. J. F. Williams, analyst. Op. cit., p. 227. 

 II. Jacupirangite, Magnet Cove. H. S. Washington, analyst. 



III. Jacupirangite, Jacupiranga, Sao Paolo, Brazil. H. S. Washington, analyst. 



IV. Pyroxenite, Brandberget, Gran, Norway. L. Schmelck, analyst. W. C. Brogger 

 Q.J. G. S., Vol. L, p. 31, 1894. 



'FeS,. 



