false amethyst, when it has the transparency of this gem.
is procured principally from England and the United States of America.
It is also found in Germany and Italy ; that which is found in the
tufa beds is beautiful and always amethystine.
Derbyshire fluorine is cut into large vases, obelisks, columns, plates,
and candlesticks, a quality being used which is indigenous to England,
and with colours arranged in zones.
Fluorine was certainly known to the ancients, who made of it very elegant balsamari.
Some people think that this may have been the same substance as the celebrated murrina, of
which so much has been spoken, without any decision as to its material
having been arrived at. Nevertheless, it seems to me impossible with
certainty to establish the identity of murrina with fluorine from the
description of their qualities given by Pliny the elder, and this,
especially, because to fluorine, which emits no smell, the sentence, " est aliqua in odore commendatici," is not suitable ; nor to a stone, tolerably hard, does the following apply : " ob amorem abroso ejus margine," which the same Pliny affirms of the murrina.
In any case, the ancients were ignorant of the valuable qualities of this stone.
till the year 1600 of our era was it adopted as a corrosive, and in
1670 the art of engraving on glass, with its assistance, was practised