. Annual report . nite to leucoxene. The quartz is in graphic intergrowth with feldspar. It istherefore classed as a quartz-diabase, the plagioclase having crystallized out beforethe augite, giving the ophitic texture. A thin section near the northwest corner of the University mine shows the rock tobe a quartz-diabase. The quartz, however, is not such a prominent constituent as insections from other parts of the area. The plagioclase occurs in the usual rods, show-ing albite twinning lamella? and giving extinction angles (in the zone normal to thetwinning lamellae) up to 36 degrees. The augite
. Annual report . nite to leucoxene. The quartz is in graphic intergrowth with feldspar. It istherefore classed as a quartz-diabase, the plagioclase having crystallized out beforethe augite, giving the ophitic texture. A thin section near the northwest corner of the University mine shows the rock tobe a quartz-diabase. The quartz, however, is not such a prominent constituent as insections from other parts of the area. The plagioclase occurs in the usual rods, show-ing albite twinning lamella? and giving extinction angles (in the zone normal to thetwinning lamellae) up to 36 degrees. The augite occurs in allotriomorphic grains, showingtwinning parallel to both 101 and 001, the latter repeated, resulting in the basal lamin-ation already described in other augites. Biotite is present sparingly. A few grainsof magnetite occur. The texture is ophitic. (b) The diabase area between Kerr and Peterson lakes (on the south and north) andbetween Cross lake and the west face of Mount Diabase (on the east and west).. Fig. 44.—Quartz-diabase, showing plagioclase (labradorite P, embedded in a micro-graphic intergrowth of quartz and feldspar. From Diabase point, Giroux lake. A specimen near the northeast corner of the Silver Leaf mine is a normal diabasesimilar to others already described. Northeasterly from this point about half a mile, aspecimen was collected near lake Cyril. It consists of labradorite in the usual rods,augite showing the basal lamination so commonly found, biotite in accessory amount,magnetite, and quartz in graphic intergrowth with feldspar. The labradorite is badlydecomposed, while some of the augite has been altered to uralite. There seems to be,however, some original hornblende present. The ophitic texture is well marked, plac-ing the rock with the quartz-diabases. (c) The diabase north of Peterson specimens may be obtained from the creek at the point where it leavesPeterson lake. The lake has been partly drained here by a small canal cut in thero
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectminesandmineralresou
