54 



thin section of one of these darker coloured 

 varieties shows the rock to be a hornblende 

 ijolite composed essentially of nepheline and a 

 deep green hornblende. Oligoclase and sphene 

 are very subordinate accessory constituents. 

 In addition to these constituents, a considerable 

 amount of calcite in large allotriomorphic indi- 

 viduals is also present, which is identical in 

 character and mode of occurrence with that so 

 commonly found in the nepheline rocks of this 

 region. This calcite is especially abundant in a 

 large exposure of the rock 25 paces west of the 

 siding to the saw mill already mentioned. 

 Another variety has a pseudoporphyritic struct- 

 ure, due to the development of larger, some- 

 what irregularly shaped individuals of nepheline 

 through a fine-grained, almost black matrix, 

 composed of deep green pyroxene and brown 

 garnet. A little microperthite and calcite occur 

 as accessory constituents, the latter mineral 

 occurring as already described. 



The New York Graphite Co. are reported to 

 be erecting a mill about a mile from Mumford 

 to treat the graphite secured from what is said 

 to be a large and rich deposit of this mineral 

 occurring in association with hornblende and 

 pyroxene gneisses. In a cutting for the railway 

 near the west end of Cardiff lake, the limestone 

 of the Grenville series is again exposed, holding 

 at this place both graphite and chondrodite. 

 Further west, near the east end of Dark lake, 

 the rock is cut by veins composed of orthoclase, 

 biotite, calcite, etc., which were formerly 

 worked for mica. 

 342-37 m. Wilberforce. Alt., 1,194 ft. (363-9 m.). — 

 551 km. Graphite occurs in many places in the Grenville 

 limestone which underlies this district, and a 

 large mill for the separation of this mineral has 

 been erected here by the Virginia Graphite Co. 

 There is an outcrop of highly graphitic lime- 

 stone adjacent to the mill. This limestone 

 contains, in addition to the graphite, a small 

 amount of colourless pyroxene, microcline and 

 sphene. The graphite-bearing rock — a graphitic 



