292 REPORT OF NATIONAL MUSEUM, 1899. 



occur associated with the mica, but at other times these are apparently wanting. 

 As in the case of apatite deposits, mica occurring in this condition would apparently 

 be found at almost any workable depth. 



2. In pyroxene rocks near the contact of cross-dikes of diorite or feldspar, the 

 action of which on the pyroxene has led to the formation of both mica and apatite. 

 Numerous instances of this mode of occurrence are found, both in the mines of 

 apatite and mica, the deposits of the latter in certain areas being quite extensive 

 and the crystals of large size. 



3. In pyroxene rock itself distinct from the contact with the gneiss. In these 

 cases the mica crystals, often of large size but frequently crushed or broken, appar- 

 ently follow certain lines of faults or fracture. Some of these deposits can be traced 

 for several yards, but for the most part are pockety. Some of these pyroxene masses 

 are very extensive, as in the case of the Cascade mine on the Gatineau river and 

 elsewhere in the vicinity. In these cases calcite is rarely seen and apatite is almost 

 entirely absent. When cut by cross-dikes conditions for the occurrence of mica or 

 apatite should be very favorable. 



4. Dikes of pyroxene, often large, cutting limestone through which subsequent 

 dikes of diorite or feldspar have intruded as in Hincks township. The crystals 

 occurring in the pyroxene near to the feldspar dikes are often of large size and of 

 dark color, resembling in this respect a biotite mica. 



The mica found under the conditions stated above, in one, two, three, and four 

 is all amber-colored and of the variety known as phlogopite, or magnesia mica. 

 [Specimens Nos. 30763, 62149, U.S.N.M.] 



5. In feldspathic-quartzose rocks which constitute dikes often of very large size, 

 cutting red and greyish gneiss, as at Villeneuve and Venosta. These are distinct 

 from the smaller veins of pegmatite which occur frequently in the gneiss as the 

 anorthosite areas are approached. In this case the mica is muscovite or potash mica 

 and is invariably found in that portion of the dike near the contact with the gneiss. 

 The crystals frequently are of large size and white in color, associated with crystals 

 of tourmaline, garnet, et cetera, but with no apatite, unless pyroxene is also present. 



6. In quartz-feldspar dikes cutting crystalline limestone, in which case the crystals 

 are generally of small size, mostly of dark color and of but little value. 



In the case of the amber micas this peculiarity was noted that when the pyroxene 

 was of a light shade of greenish gray and comparatively soft, the mica was cor- 

 respondingly light colored and clear, and in some places almost approached the mus- 

 covite in general appearance. As the pyroxene became darker in color and harder 

 in texture, the mica assumed a correspondingly darker tint and a brittle or harder 

 character, and in certain cases where dikes of blackish hornblendic diorite were 

 present the mica also assumes a black color as well. 



The chief Canadian localities, as given by the authority quoted, are 

 as below: 



Along the Ottawa Eiver it is found from a point nearly 100 miles west of Ottawa 

 to the township of Greenville, 60 miles east of that city, while on the Gatineau 

 River, which flows into the Ottawa at the city of Ottawa, mines have been located 

 and worked for 80 miles north from its mouth, and the mineral is reported from 

 points many miles farther north along that stream. To the east of Quebec it is 

 known on the branch of the Saguenay called the Manouan and in the townships of 

 Escoumains, Bergeronnes, and Tadoussac, situated east of the mouth of that river, 

 as well as at several other places along the river St. Lawrence. The mica found in 

 this last district is chiefly muscovite. 



The principal areas where mica is at present worked are in the belt which extends 

 from North Burgess, in the Province of Ontario, approximately along the strike of the 

 gneiss, into the territory adjacent to the Gatineau and Lievre. Over much of this 



