1911 Encyclopædia Britannica/Amazon-stone

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AMAZON-STONE, or Amazonite, a green variety of microclinefelspar. The name is taken from that of the river Amazon, whence certain green stones were formerly obtained, but it is doubtful whether green felspar occurs in the Amazon district. The modern amazon-stone is a mineral of restricted occurrence. Formerly it was obtained almost exclusively from the neighbourhood of Miyask, in the Ilmen mountains, 50 m. S.W. of Cheliabinsk, Russia, where it occurs in granitic rocks. Of late years, magnificent crystals have been obtained from Pike's Peak, Colorado, where it is found associated with smoky quartz, orthoclase and albite in a coarse granite or pegmatite. Some other localities in the United States yield amazon-stone, and it is also found in pegmatite in Madagascar. On account of its lively green colour, it is cut and polished to a limited extent as an ornamental stone. The colour has been attributed to the presence of copper, but as it is discharged by heat it is likely to be due to some pigment of organic origin, and an organic salt of iron has been suggested. (See Microcline.)