68 THE ROYAL SOCIETY OF CANADA 



Biotite is present as allotriomorphic individuals, and shows the 

 same associations with calcite and monticellite as before. The 

 accessory minerals, brookite, perovskite, and black iron ore again 

 occur, and the groundmass is composed of monticellite, and calcite. 



General Statement. — The rock is, therefore, composed essentially 

 of phenocrysts of olivine, augite, and biotite in a groundmass consist- 

 ing of monticellite. If this groufiidmass contained melilite, the rock 

 would be a typical alnoite, whereas if the groundmass were analcite 

 or glass, it would be classed with the monchiquites. To introduce a 

 new term would serve no purpose other than to overburden an already 

 voluminous nomenclature, and the rock will simply be termed a 

 monchiquite. 



After the formation of the iron-titanium accessory minerals 

 and the ferro-magnesian constituents, the magma contained a large 

 proportion of the lime and alumina and a considerable amount of 

 carbofi dioxide. The chrysolite was partially resorbed in this magma, 

 giving rise to a partial replacement by monticellite, while calcite and 

 chlorite were formed later, by hydro-thermal action. 



Spec. grav. 3.16. 



