REPORT OF TEE CHIEF ASTRONOMER 



311 



SESSIONAL PAPER No. 25a 



The phenocrysts are pale green augite (up to 1-5 mm. in length), a few 

 biotite foils, up to 1 mm. in diameter, and abundant round masses of serpentine, 

 almost certainly derived from olivine. The latter measure 1 to 2 mm. in 

 diameter. The ground-mass is composed of a multitude of idiomorphic deep 

 brown biotites and a few microlites of orthoclase embedded in colourless glass. 

 The rock (specimen No. 836) is relatively fresh but chlorite and calcite are 

 secondary constituents, like the serpentine. It has the composition of an 

 olivine-augite minette, as shown by Mr. Connor's analysis: — 



Analysis of olivine-augite minette. 



SiO ? 



Ti0 2 



A1 2 3 



Fe 2 3 



FeO 



MnO 



MgO 



CaO 



SrO 



BaO 



Na,0 



K 2 6 



H 2 at 110°C. .. 

 H 2 above 110°C. 



PA 



co 2 



Mol. 



48-33 



•806 



•81 



•010 



12-56 



•124 



1-87 



•012 



5-26 



•073 



•13 



•001 



9-07 



•227 



8-94 



•160 



•05 





•24 



•001 



1-81 



•029 



4-67 



•050 



•97 





2-63 





•78 



•006 



2-64 





100-76 





Sp. gr. 



2-771 



The calculated norm is: 



Drfhoclase.. .. 



Albite 



Nephelite . . 

 Anorthite . . .. 



Diopside 



Olivine 



Ilmenite 



Magnetite.. .. 



Apatite 



Water and C0 2 



27.8(1 



8-91 



3-41 



12-51 



21-75 



13-76 



1-52 



2-78 



1-86 



6-24 



100-54 



According to the Norm classification the rock enters the dopotassic subrang, 

 prowersose, of the domalkalic rang, kilauase, in the salfemane order, gallare; 

 it is, however, near the sodipotassic subrang, lamarose, of the same rang. 



Comparison of the Minettes with the World Average. — In Table XVIII. 

 the three minette analyses are entered and, as well, their mean and ihe average 

 of ten analyses recorded for the world in Osann's compilation. 



