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268                       GEMS AND PRECIOUS STONES IN THE
several inches in diameter and of rich color, showing blue opalesĀ­cence, at Morin, Que.
The beautiful variety of albite called peristerite, exhibiting a peculiar bluish chatoyancy or opalescence, is sometimes mingled with pale green and yellow, and called " moonstone." It is found in crystals and in large cleavable masses, containing disseminated grains of quartz, in veins cutting the Laurentian strata at Bath-urst, Ont., on the north side of Stony Lake, near the mouth of Eel Creek; in Burleigh, Ont., in crystals, in large, opalescent, cleavable masses of reddish albite, and north of Perth, Ont. It is also reported by Mr. G. Christian Hoffmann, of the Canadian Geological Survey, in specimens showing beautiful blue color, from Villeneuve, Ottawa County, Que.
Perthite occurs in large cleavable masses in thick pegmatite veins, cutting the Laurentian strata, and is often made up of flesh-red and reddish-brown bands of orthoclase and albite, interlami-nated. When cut in certain directions, it shows beautiful golden reflections like aventurine, and being susceptible of a high polish, is adapted for an ornamental stone or for use in jewelry. It is also found in considerable quantity at Burgess, Ont, about seven miles southwest of the town of Perth, and likewise near Little Adams Lake.
Sunstone, aventurine feldspar, has been described by Dr. Bigsby in the form of a largely crystallized flesh-red feldspar, constituting part of a granitic vein traversing gneiss, twenty miles east of the French River, on the northeast shore of Lake Huron, and occurs in fine specimens at Sebastopol, Ont.
Obsidian has been found in British Columbia, but it has litĀ­tle value except for the cheaper jewelry, and even then is rarely used for such purposes.
The porphyries which cut the Laurentian limestones in the townships of Grenville and Chatham, Que., form a dike running east and west twenty feet in breadth. They have a dark-green or brownish-black base, homogeneous and compact, containing crystals of red orthoclase, and admitting of a high polish, which strongly recommends the material for ornamental use.
The pegmatite at Montgomery's Clearing on Allumette Lake, five miles above Pembroke, Ont., consisting of a brownish-