540 OGILVIE 



Lincolnose. II. 5. 3. 2. As already mentioned this new name 

 is proposed for the soft rock which forms the core of both in- 

 trusions. Megascopically it is seen to contain large blue augen 

 set in a ground-mass which is dense and dark except for mica 

 scales. 



Microscopic Character. — The augen are found to be in all 

 respects similar to those already described, and are of the least 

 crushed variety. In the ground-mass are found biotite, 

 pyroxene, hornblende, titanite and magnetite, with a very little 

 microcline, and more plagioclase, which is partly labradorite 

 and partly albite, and a little microperthite. 



There are three types of pyroxene. One of these is an ordinary 

 colorless or greenish augite, remarkable only for its inclusions. 

 The inclusions are opaque black grains or rods, probably of 

 titaniferous magnetite, and are so abundant as to make the 

 augite appear opaque. Prismatic faces are occasionally present 

 in this augite, but terminal faces are lacking. About the edges 

 there is frequently an intergrowth of biotite along the cleavage 

 cracks, and biotite and brown hornblende together frequently 

 form rosettes which seem derived from the augite by dynamic 

 metamorphism. 



The second type of pyroxene is faintly pleochroic from pink to 

 violet and has an extinction angle (measured from C in the plane 

 010) which varies from o° to 13 . In addition to the ordinary 

 pyroxene cleavage, a parting parallel to 100 can be plainly 

 seen, and a less distinct parting parallel to 010. These properties 

 seem most nearly to correspond to diallage. This mineral 

 contains great quantities of brownish red inclusions, apparently 

 both rutile and titaniferous magnetite being present. Crystal 

 boundaries are lacking in the diallage. It is usually surrounded 

 by biotite and brown hornblende. 



The third type of pyroxene is apparently secondary, the 

 result of dynamic metamorphism of either of the two preceding 

 types, and is usually associated with the rims of biotite 

 and hornblende. It occurs in irregular grains, without in- 

 clusions, is frequently twinned, and is occasionally altered to 

 uralite. 



The hornblende is reddish brown and occurs in two ways. 



