believe that this difference is more the result of a diiferent
composition of the stone than of the error of chemists, as in
experiments I have been able to observe that all lapis lazuli do not
present the same characteristics. Thus, those that come from Persia
and China unite to a finer colour an equal and very fine texture,
almost similar to that of the agate ; and its hardness is greater than
of that found in the Siberian steppes, which to a darker colour unites
a granulated texture, and is of a much inferior quality. "Whence I
believe that some comparative experiments would help to explain the
cause of so much diversity, and render it possible to divide the lapis
lazuli, like other gems, into Oriental and Western.
gem, when exposed to a strong heat, melts into a yellowish-black mass.
Under the action of the blowpipe it forms a white crystal, but, when
mixed with borax, it melts with effervescence into a very clear crystal.
As I have remarked, the most beautiful come from