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CHAPTER XXI.
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LAPIS-LAZULI.
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HIS stone is remarkable for its beautiful blue colour, whence the Arabians call it Azul, meaning
"blue." Theophrastus describes a blue stone "spotted with gold dust,"
while Pliny speaks of it as being "like to the serene blue heavens,
fretted with golden fire." The " gold " mentioned by these and other
ancient authors refers to the spangles of brassÂlike iron-pyrites which
are commonly dispersed through the rich blue substance of the
Lapis-Lazuli.
The
colour of the stone varies from pale azure to deep blue, with a tint of
green ; but is seldom quite pure, being often mottled with white and
yellow spots. Indeed, the Lapis-Lazuli is not a homogeneous substance,
but consists of a definite blue mineral, which is probably referable to
the species Haiiyne, associated with a colourless substance,
whence its mottled appearance. It is brittle, has but little lustre,
and is translucent only at the corners of thin edges. The precise
origin of the beautiful blue colour of the Lapis-Lazuli is still a
matter on which chemical opinion is divided. It is usually referred to
the presence of a sulÂphide, probably of sodium and iron, but it
appears likely that the sulphur is present in the form both of a
sulphide
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