338 F. Z. Ransome — Apatitic Minette. 



sition. The pyroxene is for the most part fresh, but some 

 crystals have undergone slight partial alteration into green 

 hornblende and calcite. The apatite occurs in stout prisms up 

 to two millimeters in length and is noticeably abundant as seen 

 in thin sections. It is included chiefly in the orthoclase and 

 biotite, although the augite is not free from occasional prisms. 

 Rather abundant titanite and a little magnetite and pyrite 

 make up the minor constituents. 



• The chemical analysis of this rock by Dr. Hillebrand is as 

 follows : 



Chemical Analysis of Minette. 



Si0 2 



A1 2 3 



Fe 



41-57 



9*75 



4-06* 



F 



Cr 2 3 



NiO _. 



•23 



•04 

 •02 



FeO 



M^O 



CaO 



4-47* 



8-65 



11-10 



T57 



6-10 



MnO.. 



BaO 



SrO 



•25 

 •44 

 •11 



Na 2 



K O 



Li 2 ,_ 



V'O, 



trace 



•04 



2 



HO- 



1-54 



2 3 



FeS 2 



Less O for Fl, CI, .. 



•06 



H O-f 



2*30 





TiO a ..._ 



ZrO . _ 



2-36 



. -02 



100-01 



•11 



co 2 



P 2 5 



CI 



1-24 



... 4-05 



-04 





99-90 



In comparison with most minettes the analysis of the rock 

 here described is low in silica and alumina, rather high in 

 potash and titania, and remarkably high in phosphoric acid. 

 This last feature, indeed, is the most noteworthy peculiarity of 

 the rock. Out of the 2112 rocks of which superior analyses 

 are collected in Washington's tablesf only 59, or 2*7 per cent, 

 contain over 1 per cent of P 2 5 . Of these only 10 contain over 

 2 per cent, and, of these 10, only 2 have over 3 per cent of P 2 5 , 

 namely a pyroxene-apatite-syenite (orendase) from Finland, 

 described by Hackman,^: with 5*98 per cent of P 2 5 and an 

 avezacite (avezaciase) from the Pyrenees described by Lacroix§ 

 with 3-32 per cent of P 2 5 . 



The norm as calculated from the chemical analysis and the 

 place of the rock in the quantitative classification are as 

 follows : 



* Not corrected for influence of V 2 3 . 



f Washington, H. S. Chemical analyses of igneous rocks. Professional 

 Paper U. S. Geol. Survey No. 14, 1903 ; Superior analyses of igneous rocks. 

 Professional Paper TJ. S. Geol. Survey No. 28, 1904. 



% Hackman, V. Neue Mittheilungen iiber das Ijolithmassiv in Kuusamo. 

 Bull, commission Geologique de Finlande No. 11, 1899, pp. 36-37. 



§ Lacroix, A.. Les roches basiques accompagnant les lherzolites et les 

 ophites des Pyrenees. Comte Eendu VIII Congres Ge*ol. Int. 1900, Paris, 

 1901, p. 382. 



