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

CERYSO PRASE. 71It is generally transparent and sometimes opaque, oflittle brightness although it takes a good polish.Itscleavage is united and resrnous. Its hardness is somewhatless than that of the calcedony. It is coloured bynickel, and when subjected to a great heat it loses itstint.It is found in small veins or lines of about fifteen millimetresin thickness, interrupted by a green earth containingnickel. Its analysis presentsSilex 96-16Lime 0-83Alumina 0'08Oxide of iron 0'08Oxide of nickelI'OOIts specific weightis 2 5.The mineralogical strata of the chrysoprase are immediatelyunder the vegetable earth, at two or threefeet depth sometimes it is procured in the clefts of;the rocks, inclosed in a kind of asbestos. It is full ofdeep cavities, like the malachite.The, chrysoprase, unlike all other gems, is only foundin Europe, and even there in but one country, that ofPrussia, in the province of Silesia, in a part of thecountry called Kosemuth, situated on the mountain ofGlasendorf, and at Stachlan, near Cologne ;and for thisreason it is commonly called " Prussian grey." As italways presents chinks intermingled with grains, it isnot easy to understand the union of its heterogeneousparts.