204 Professor T. G. Bonneij — A Socialite Syenite 



the latter sometimes showing only a change in a green tint, but 

 occasionally passing from a fairly strong green to deep brown. 

 I have not found an extinction angle exceeding 12°. The larger 

 crystals include sphene, and once or twice a small grain of felspar. 

 (4) Sodalite, not abundant or blue ; in little interstitial patches 

 of granules. (5) Sphene, rather abundant ; obviously the first 

 mineral to consolidate, for it is idiomorphic, and is included by or 

 penetrates the hornblende. The specific gravity of this specimen is 

 also 2-58. 



Two small fragments "from boulders" are varieties (not quite 

 so well preserved) of a similar rock, but are more gneissic in 

 structure and contain, especially one of them, rather more dark 

 pyroxene. Examination of thin slices shows three forms of this 

 mineral : a slightly pleochroic (gi'een to pale brown) augite, probably 

 osgirine, a brown hornblende, and a green one (both as described 

 above). The third seems formed from the second, but in one case 

 also from a puce-brown augite (? titaniferous). A more normal 

 orthoclase is common among the felspars, but microperthite and 

 plagioclase are found. Nepheline is much less abundant than in the 

 last specimen, but certainly occurs. There is a little sodalite, once 

 or twice seeming to fill a crack, a grain or two of iron-oxide, some 

 apatite, and a fair amount of sphene, these two being the first to form. 



The fourth specimen has a dark-green groundmass, slightly mottled 

 with a paler tint (which becomes yellowish-white on a vvreathered 

 surface). In this ai-e scattered grains, a little more than -3" in 

 diameter, of a brownish - black pyroxene, with slight traces of 

 a lustre - mottling. A slice proves the constituent minerals to be 

 (1) a pleochroic augite, changing from a pale brownish-yellow to 

 puce brown (probably a titaniferous variety), showing locally 

 a diallagic habit by small dark parallel lines or rods, which M^hen 

 highly magnified appear a deep brown colour ; a second set, making 

 a large angle with these, being sometimes visible. (2) A green 

 pyroxene in fair-sized grains, which, however, show a mottled or 

 composite structure, probably a further stage of change. (3) A 

 strongly pleochroic hornblende, changing from warm brown to deep 

 brown. The relation of these pyroxenes is not easily determined. 

 Sometimes a small grain of the augite seems to be included in the 

 hornblende, sometimes the two lie side by side with a sharp line of 

 ilemarcation, the crystals in each case having different orientations; 

 but sometimes films or spots of the brown hornblende are connected 

 either with augite of similar colour or with the green aggregate, as 

 if formed from them. The brown augite is occasionally composite 

 in structure, so 1 incline to regard these as a series of changes of 

 which the brown hornblende is the last. (4) Iron-oxide : generally 

 associated with the pyroxene, and later in consolidation, often en- 

 closed in a very narrow, clear, composite border. (5) Apatite: very 

 characteristic and rather abundant, generally containing some dusty 

 material. (6) Nepheline, in ii-regular grains, acting as a sort of 

 matrix to the pyroxene, containing sometimes minute colourless 

 needles, and not seldom films similar to those already mentioned in 



