and in cut form : two of the latter weigh respectively, 43 and 34 carats.
is one of the five species of precious stones which contain the earth
glucina as an essential constituent—the others are beryllonite,
euclase, beryl, and chrysoberyl. Its percentage composition is
represented by the numbers :
is rarely used as a gem stone. It varies in hue from a pale straw
colour through many qualities of green to indigo blue. Its hardness is
7*5, and its specific gravity about 3-1. It crystallises in the
monoclinic system, and exhibits trichroism. Fine crystals came from
the neighbourhood of Villa Rica, Brazil, where it was associated with
topaz in a chloritic schist. It occurs in the Urals. Its composition in
100 parts is approximately :
Traces of iron, lime, tin and fluorine occur in euclase.
another mineral species containing the earth beryllia ( = glucina) has
been cut occasionally as a gem stone. It is a sodium glucinum
phosphate, and crystallises in the rhombic system. It occurs at
Stoneham, Maine, U.S.A. Beryllonite is transparent and colourless and
presents no valuable optical characters entitling it to rank as a
precious stone. It is, moreover, brittle and of no more than 6 degrees
of hardness. But to the chemist its strange composition is
interesting, while to the crystallographer its complex forms appeal.
gem-stones known as jargoons as well as the true hyacinths or jacinths
belong to the same mineral species. There are many circum-stances which
unite to make the zircon a beautiful and interesting