sis of a
specimen of Brazilian chrysoberyl gave alumina 78.10, beryllia 17.94,
and ferric oxide 4.88%. The typical yellow colour of the stone inclines
in many cases to pale green, occasionally passing into shades of dark
green and brown. The iron usually present in the mineral seems
responsible for the green colour. Chrysoberyl is often mistaken by its
colour for chrysolite (q.v.), and has indeed been termed Oriental
chrysolite. In its crystalline forms it bears some relationship to
chrysolite, both crystallizing in the orthorhombic system, but it is a
much harder and a denser mineral. As the two stones are apt to be
confounded, it may be convenient to contrast their chief characters:--

Chrysoberyl. Chrysolite.
Hardness 8.5 6.5 to 7
Specific Gravity 3.65 to 3.75 3.34 to 3.37
Chemical Composition BeAl2O4. Mg2SiO4.

Chrysoberyl is not infrequently cloudy, opalescent and chatoyant, and is
then known as "cymophane" (Gr. [Greek: kyma], a "cloud"). The cloudiness
is referable to the presence of multitudes of microscopic cavities. Some
of the cymophane, when cut with a convex surface, forms the most
valuable kind of cat's-eye (see CAT'S-EYE). A remarkable dichroic
variety of chrysoberyl is known as alexandrite (q.v.).

Most chrysoberyl comes from Brazil, chiefly from the district of Minas
Novas in the state of Minas Geraes, where it occurs as small water-worn
pebbles. The cymophane is mostly from the gem-gravels of Ceylon.
Chrysoberyl is known as a constituent of certain kinds of granite,
pegmatite and gneiss. In the United States it occurs at Haddam, Conn.;
Greenfield Centre, near Saratoga Springs, N.Y.; and in Manhattan island.
It is known also in the province of Quebec, Canada, and has been found
near Gwelo in Rhodesia. (F. W. R.*)

CHRYSOCOLLA, a hydrous copper silicate occurring as a decomposition
product of copper ores. It is never found as crystals, but always as
encrusting and botryoidal masses with a microcrystalline structure. It
is green or bluish-green in colour, and often has the appearance of opal
or enamel, being translucent and having a conchoidal fracture with
vitreous lustre; sometimes it is earthy in texture. Not being a definite
crystallized substance, it varies widely in chemical composition, the
copper oxide (CuO), for example, varying in different analyses from 17
to 67%; the formula is usually given a