[HARViE] PALAEOZOIC BRECCIA OF THE VICINITY OF MONTREAL 257 



sorbed by the molten material and then when later weathering had re- 

 moved the interior of the nodule, a cavity was formed lined with th^ 

 crystals of mica, pyroxene, magnetite, etc., which occur in the limestone. 

 The sections show the intrusive to consist essentially of phenocrysts 

 of augite, olivine and biotite, in a fine-grained gray groundmass. 

 The augite is the most important constituent, occurring in large crystals 

 up to half an inch in size. The individuals are pink to pale green in 

 colour and show high dispersion of the axes with marked zonal structure. 

 The edges have been corroded by the magma and are now very dusty, 

 almost opaque. With a high power objective, these rims are seen to be 

 composed of mica with leucoxene or sphene dust. One of the hand speci- 

 mens shows a large individual of pyroxene an inch and a half long, with 

 a strong marginal reaction zone. Its outline is much rounded, but it is 

 considered to be a phenocryst also. Olivine is next to the augite in im- 

 portance being also found in huge phenocrysts, commonly an inch across; 

 some grains now separated are apparently fragments of one original 

 gigantic individual. The forms are very irregular owing to the resorp- 

 tion action of the magma, which has also produced very pronounced rims, 

 —some semi-opaque like the augite, others transparent due to a variation 

 in composition of the outer portion. The biotite occurs in occasional 

 large plates up to half an inch across. It is surrounded by a dense border 

 of magnetite grains. The forms are much corroded and several instances 

 show the reaction working into the heart of the crystal favoured by the 

 strong cleavage of the mica. A second generation is present in the paste. 

 Felspar,— a basic labradorite, is present as a few individuals. Apatite 

 occurs in two generations. An unknown mineral, at first taken for apa- 

 tite, is found in small amount. It has the same low refraction, dull 

 polarisation and colour, but is monoclinic, with an extinction up to 43°. 

 A second unknown mineral also occurs in small amount, being well pre- 

 served as short prisms with good outlines, showing slight cleavage, and 

 having an inclined extinction up to 45°. It has a refraction distinctly 

 higher than that of calcite and polarises in dull blue to pale yellow tints. 

 Ilmenite is extremely abundant in both large and small crystals, fre- 

 quently showing cross hatching; pyrite and pyrrhotite are also present. 

 Perovskite is quite plentiful in very fresh minute octahedra. One amyg- 

 dule was observed filled with a zeolite considered to be natrolite. The 

 base is made up of a dull polarising, somewhat granular mineral, having 

 parallel extinction and staining readily after etching. It is undoubtedly 

 nepheline. Except for the lack of melilite, this rock corresponds very 

 closely to an alnoite. 



The third occurrence is a dyke about twenty-five feet wide, which 

 may be followed by occasional outcrops for a distance of half a mile. 



