XXIX.
CHRYSOBERYL.
This mineral
is of an asparagus-green colour, crystallized in prisms of eight
sides, crowned by a kind of small cupola having six facets, which
subdivide occasionally in as many more little facets ; notwithstanding
which, its primitive form may be said to be a prism with four
rectangular faces.
The
hardness of the chrysoberyl is almost equal to that of the corundum.
Its light is very bright ; it breaks easily ; is semi-transparent ;
does not melt under the action of the blow-pipe; has but slight double
refraction; becomes electrical; its cleavage is double, and its
specific weight from 3-60 to 3-76. When analysed it yields, according
to Barbot,
