Gems Notes and Extracts Augusto Castellani, Mrs. John Brogden 1871

EMERALD. 205Silex 68-50Alumina .. .. 15 '75Glucine .. .. .. 12 '50Protoxide of iron . . 1 00Earth 0-25Oxide of chrome .. 30Magnesia.. .. Traces.Soda .. .. .. Traces.It is not corroded by acids, but issoluble in salts ofphosphorus. It is found in micaceous schists at Salzburg,in the mountains of Sahara, in the argillaceousearths of Peru and of Siberia, at Henbachthal, in Germany,at the height of 8,700 feet above the level of thesea.The Western emerald is now procured principallyfrom America, where the mines of Muzo, in Xew Granada,are celebrated.Emeralds of very good quality are dug up at Odontchelong,in Siberia, and at Ava, in India.This gem has often imperfections and flaws insidewhich quite deprive it of its lustre ;there are some,too, very opaque.It has been thought that the greenemerald is derived from oxide of chrome ;colour of thebut Levy, inthe analysis, perceiving such a small quantity ofchromic acid, formed theopinion that it was producedby some organic substance, which he imagined was acarburet of hydrogen similar to the chlorophyll whichcolours the leaves of plants.