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

PEASE. 185It takes a polish which would be perfectif it wasnot resinous, and which it losesin the course of time.Its colour, quite different from that of the plasma,which is rather olive, is of a decidedly emerald green.Small and rare are the pieces of pure prase, as thisstone isalways mixed and marked with lime, and itsinternal crystallization is not homogeneous or perfect.When it presents the appearance of a regular crystalit takes the form of a prism or pyramid, having sixfaces of medium size ;its external surface isrough andnot very bright, but the breakage is scaly, concave, andof a vitreous light.The prase in block is often formed of pieces stucktogether, whose faces, somewhat rough, are obliquelylined.This mineral, which has a specific gravity of 2-67,yields on being analysedSilex 92-5Alumina .. .. .. 0*5Glucine .. .. .. 4' 5Magnesia . . . . . . 1 'Oxide of iron .. .. 0'5Oxide of nickel . . . . 1 'The ancients believed prase to be a kind of imperfectemerald, and besides the name of prasium, they alsocalled it smamgdoprasium ; but no one has left anexact description of it ;and Theophrastus, who succeededAristotle, made greater confusion by giving thename of smaragdus to every kind of green stone. This