65 



Order of Consolidation. 



Chromite 

 Olivine 

 Diallage 

 Enstatite 



The tachylytic coating consists essentially of a light-brown 

 glass crowded with magnetite grains, rendering it almost 

 opaque. A few partially-absorbed grains of olivine and augite 

 are scattered about with little or no felspar. 



The nodules under consideration are thus plutonic in 

 origin and allied to the Enstatite Peridotites. 



Chemical Composition. 



Two very concordant analyses were made by the author 

 and a mean taken. 



The usual methods recommended by Hillabrand and Wash- 

 ington were followed. The ferrous iron, however, was deter- 

 mined by the method recommended by P. G. Wykeham 

 Bayly, (2) viz., by heating one gram of the substance in a 

 covered platinum crucible with H 2 S0 4 (1-1) and HF for ten 

 minutes on an iron plate, and then titrating with standard 

 permanganate of potash. Several determinations were made 

 with and without the use of C0 2 with satisfactory results. 

 Combined water was determined by the Penfield method, and 

 the usual colourometric methods for titanium and chromium. 

 Barium and strontium were not determined spectroscopically. 



Results of Analysis. 



The Norm 





Si0 2 



. 45-22 



Orthoclase ... . 



Ill 



A1 2 3 



.. 2'99 



Albite 



4-72 



Fe 2 3 



•20 



Anorthite 



4-73 



FeO 



7-17 



Diopside 



3-07 



MgO 



. 40-89 



Hypersthene 



. 14-72 



CaO ... ... . 



1-93 



Olivine 



. 70-44 



Na 2 



•55 



Magnetite 



•23 



K 2 



•21 



Ilmenite 



•30 



H 2 0+ 



•20 



Apatite 



•31 



H 2 0- 



•05 



Chromite 



•22 



C0 2 



nil 



Water .. 



•25 



TiO, 



•14 









p 2 o: 



•20 





100-10 



Cr 2 3 



•20 







NiO,CoO ... . 



•14 







MnO 



•28 







BaO 



nil 







SrO 



•04 

 100-41 







<2) Recent Methods of Rock Analysis, A.A.A.S., 1907. 



