234	PRECIOUS STONES.
	of the finest specimens known. The place where they were first worked by Europeans, and whence they had been pre­viously obtained by the natives, was at Somondoco on the eastern slopes of the Cordillera of Bogota ; these deposits, though still sometimes worked, do not yield very fine quality stones. Afterwards another deposit was found on the western slopes of the Eastern Cordillera to the east of the Rio Magdalena and near the town of Muzo, lying to the north of the capital, Bogota. This is now the principal locality in which the gem is found ; the mineral occurs in a dark bituminous limestone, and the crystals are usually implanted on Calcite, the latter occurring in cavities in the limestone (Fig. 21). This deposit is of interest in another way, because it practically forms the only exception to the rule that Emerald occurs in granitic and dynamo-meta-morphic rocks. The associates are exceptional also, Gypsum, Pearlspar, Quartz, Iron Pyrites, and a rare mineral called Parisite being found with the Emerald. Many of the specimens show the dislocations, but in this case the material filling the fissures is Calcite and not Quartz. The stones, too, are prone to become turbid after a time from the formation of numerous minute flaws. Emeralds of gem quality are known locally as Canutillos, and those not fit for cutting as Morallons. Also in South America, in Brazil, Beryl occurs in some quantity in the north-east of Minas Geraes, associated with Topaz and Chrysoberyl ; the crystals are often of several pounds weight, but the larger ones are usually, as else­where, cloudy and in a large part unfit to cut. The mineral here is probably derived from a granitic rock. Near Bio de Janeiro, too, Beryl occurs in pegmatite bands