254 THE CANADIAN NATURALIST. [Vol. ix. 



ance is seen. Along some of the cracks an alteration to serpentine 

 has taken place, while along others a little red oxide of iron is 

 visible. Although the amount of this peroxide is small as shown 

 both by the microscope and by anal^^sis, it is nevertheless, evi- 

 dently the cause of the general red colour which the mineral has 

 assumed. 



Another locality in which olivine has recently been found is a 

 short distance to the south-east of Mount Albert, just south of the 

 south second fork of the Ste. Anne River, Quebec. The explora- 

 tions of Mr. Richardson during the past season have shown that 

 it there forms important rock-masses close to the serpentines of 

 Mount Albert, which have evidently been produced by the al- 

 teration of the olivine. A specimen of the rock collected by 

 Mr, Richardson is fine gi-anular, slightly friable, and pale yellow- 

 ish to greyish-green in colour. It shows a few minute black 

 grains, probably of chromite, and rarely a little of a fibrous 

 mineral which resembles enstatite. Altogether, the rock looks 

 remarkably like one variety of that from North Carolina, which 

 was many years ago described by Genth, and regarded by him 

 as the source of the serpentine and talc of the same region.* 



The orio'in of such olivine rocks as those of Carolina and 

 Mount Albert is a difficult and disputed question, but one which 

 still remains, whether we believe that the serpentines which ac- 

 company them where derived from them or not. In opposition 

 to the view that they owe their origin to chemical precipitation, 

 Clarence King suggests that they may represent accumulations 

 of olivine sands like those now occuring on the shores of the 

 Hawaiian Islands. f Whether such accumulations did take place 

 in the earlier ireolooical formations we do not know, but there is 

 certainly nothing unreasonable or unlikely in the view that mag- 

 nesian precepitates may then, as in later times, have been formed 

 and subsequentl}^ altered to olivine. 



A thin section of the olivine rock or dunite from near Mount 

 Albert, when examined with the microscope, presents the appear 

 ance shown in Fiu'. 1 a. It is seen to consist almost entirely of 

 granular olivine, with occasional black grains of chromic iron. 

 Owing to an alternation of layers with finer and coarser texture, 



* American Journal of Science^ Vol. XXXIII. ; 1862, p. 199. 

 f United States Geological Exploration of the Fortieth Parallel. 

 Vol. 1.. p. 117. 



