late certain varieties of this mineral have been cut as gem-stones. Its
colours vary from greyish to greenish yellow ; some varieties are
opaque and others transparent. Although susceptible of high polish, it
is a very difficult material to work, partly because it is much harder
in one direction than another, and partly on account of its remarkably
easy cleavage, which renders it liable to split.
is found in a large number of localities, but the transparent variety,
which alone has been cut as an ornamental stone, is confined to Brazil.
The mineral previously described as Hiddenite, or " Lithia Emerald," is only a variety of Spodumene.