LYDIUS LAPIS, in the natural history of the ancients; the name of the stone used by way of touchstone for the trial of gold and silver, and called by some Heraclius lapis; both of which names were also applied by the ancients to the loadstone; and hence has arisen
Lydia no small misunderstanding of their works. Pliny has
Lyne-regis. observed, that both the leadstone and touchstone were
at times called Lydius and Heraclius lapis.
The true lapis Lydius, or the touchstone, was an-
ciently found only in the river Tmolus; but was after-
wards found in many other places, and is now very
common in many of the German rivers. The ancients
give us very remarkable and circumstantial accounts of
the uses they made of it; and it is plain they were able
to discern the alloys of gold by means of it with very
great exactness. We at present use several different
stones under this name, and for the same purpose. In
Italy, a green marble called verdello, is most frequently
used; and with us, very frequently small pieces of
basalt.