Caire saw in London a large Oriental ruby, which, when placed in the sun, gave out a luminous star, and he describes it as an asteria-ruby ;—the star-reflecting diamond of the Mineralogical Museum, in the Jardin des Plantes, in Paris, would thus be an asteria-diamond. There is in the School of Mines, in Paris, a star-reflecting opaline corundum, therefore it is also an asteria-corun-dum.
It seems to me we may conclude from the above that in the present day it is not intended to give the name of asteria to
one separate species of gem, but rather to use it as indicating the
different character of various species. The imperfect knowledge of
mineralogy possessed by the ancients did not enable them to
distinguish the different species of precious stones by their
essential characteristics; whence Pliny thought to describe and
determine one single class by a quality which is common to many.
The
phenomenon with regard to which these conclusions have been drawn is
the result of a particular combination of molecules, which may be
formed in every gem crystal; and by means of a very convex cutting, it
takes place under a given inclination. If the name of asteria is
retained, we may be certain that the most rare are corundums, and that
amongst these the azure, or sapphires, give the appearance of stars
more brilliantly.
