JV. JV. Evans — Chrysoberyl from Canada. 317 



joins the Matawin. This whole region forms part of the great 

 Laurentian peneplain and is underlain by Laurentian gneisses 

 which, in this district, hold in places a few small bands of 

 crystalline limestones. At the locality where the chrysoberyl 

 occurs, the country rock consists of a series of quartzose 

 gneisses ; these present a considerable variation in character, 

 being often highly garnetiferous, and they are associated with 

 bands of quartzites. The whole series strikes JN". 40-45° W. 

 and has a high east dip. The gneiss, where the river crosses 

 it here, is cut by great veins and dikes of pegmatite ; these 

 are composed of quartz, orthoclase and a white mica, with 

 black tourmaline and the chrysoberyl as accessory constituents. 

 The pegmatite, as is not uncommonly the case with this rock, 

 often shows a rapid variation in size of grain from place to 

 place. The chrysoberyl is not abundant, but occurs in well- 

 defined crystals. 



The rock specimen brought to Montreal contained two indi- 

 viduals of the chrysoberyl ; careful chipping brought out the 

 larger in two fragments and some small chips. The two prin- 

 cipal fragments were fitted together and weighed 55 grams. 

 This individual, about half of which is uninjured, has almost 

 exactly the form of a hexagonal prism, apparently quite similar 

 to the one figured in Dana's System of Mineralogy, 1885, fig. 

 155, terminated at each end by a hexagonal pyramid and end 

 face ; it measures an inch and a half across and an inch and a 

 quarter in the direction of the pseudo principal axis ; the faces 

 of the pseudo-prism, three of which are almost perfect, give 

 an angle of 120° with the contact goniometer (they are not 

 sufficiently smooth for more accurate measurement), and a 

 seam, running vertically through the middles of two opposite 

 prism faces, two of the pyramid faces, and the end faces, 

 seems to be a plane along which the crystal has at one time 

 been fractured, one-half having been slid along about 1/25 

 inch from its original position; there is, however, no sign of 

 diminished coherence along this plane now. The material of 

 the crystal is apparently fairly pure except for thin films of 

 iron oxide running through it, and some orthoclase which pen- 

 etrates it on one side. 



The cleanest of the chips were chosen for analysis and were 

 ground to a very fine powder in a specially hardened steel 

 mortar ; the powder was subsequently boiled with hydrochloric 

 acid, filtered, washed and dried, to free it from the very con- 

 siderable quantity of steel abraded from the mortar. The 

 method of analysis employed was a slight modification of that 

 given by Penfield and Harper in this Journal (3), xxxii, p. 114 

 (1886). After several preliminary trials, two analyses were 

 made of the mineral, in each of which about 0*15 grams of the 



