is the colour generally associated with the topaz, yet topaz is
sometimes colourless, or may present almost any colour, and beautiful
specimens of other colours are often supposed to be some other mineral,
so thoroughly identified is this stone with the colour yellow. The
sometime popularity of topaz has of late years declined, and a
probable reason is the common substitution of other stones for it.
Topaz takes its name from Topazios, meaning " to seek ";
because the earliest known locality from whence it came was an island
in the Red Sea which was often surrounded by fog, and therefore
difficult for the local mariners to find.
The name of topaz in mineralogical science is Topaz rhombicus, and,
like the opal, it belongs to the order Hyalina. The primary form of
topaz in crystallography is a right rhombic prism. Its cleavage is
parallel to its basal