XCVI.
TRIPOLI.
This mineral
substance is not a gem, although necessary to the working of gems ; and
therefore all treatises which have mentioned it, have spoken very
briefly of it.
By the ancients it was called stone of Samoa.
The name which we give to it now comes from the city of Tripoli, whence it was procured before being found in Europe.
It
is used principally in giving the last polish to precious stones, and
it is useful besides to engravers, opticians, workers in precious
metals, gun-makers, and varnishers.
It
appears that tripoli is a schist or a clay. It is found more or less
caloined, and mixed with other schists and clay. On this account it has
different degrees of hardness. ·
Analysed by Hasse, it gave
