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Labradorite
The name of the gem is derived, through the
mediev -: lapis lazulus, from the Arabic word lazward, from
wr word azure comes; but according to the descny Pliny the
Elder, the ancient Romans called it saF:The name sapphirus
was, of course, subsequently ~: . to the blue variety of corundum.
Scientifically spe-lapis lazuli is a rock," because it
consists of an a, : tion of minerals: lazurite and variable
quantities of _ : pyrite, and other feldspathoids of the socialite
grouF as haiiyne and nosean.
Appearance 1t has a uniform, massive or som•
granular appearance, with fairly distinct crystals. It is
opaque or opaque, with a surface that can take a go: ish-like
jades, for example. It is a strong but livei; sometimes with
a hint of violet. It often contains gra, off-white patches
or veins, consisting of distinct, in,ven crystals which are
minutely fringed at the edge patches, interpenetrated by and
interwoven with th• ute crystals of blue. The presence
of white patch • duces the gem's value. The most highly
prized variet,• those which are uniformly colored, preferably
wiitviolet tinge. It often contains minute, scattered crysv
- pyrite, which do not detract from its value. It is mao spherical
or curved beads and even faceted, polyr ones, in which the
flat facets can take a very good po, is also fashioned into
carved gems, boxes, mosaics ornaments, vases, and figurines,
the largest of whice be tens of centimeters in size. At one
time, it was used for sealstones. The Egyptians used it for
their ,- . drical seals.
Distinctive features The particular, very
attractive r and speckling with minute crystals of pyrite
give lapis an unmistakable appearance. As for the physical
proi ties, the density of gem-quality material is very variable
to the presence of pyrite and other foreign minerals, br.
any case, it is much higher than that of the mineral lazu•
It is normally between 2.7 and 2.9 g/cm3, but can bF much
as 3.0 g/cm3. On contact with a minute drop of drochloric
acid, lapis lazuli immediately gives off an odc hydrogen sulphide
(like the smell of rotten eggs).
Occurrence The best quality
lapis lazuli comes fr Afghanistan, where it has been mined
since remote aw uity. The ancient Egyptians probably obtained
their s, plies from there. It is also found in Chile, but
usually w numerous light patches and veins. Much smaller quar
ties come from the Soviet Union (Siberia), Burma, Pa stan,
Angola, the United States, and Canada.
Value It is one of the most valuable semiopaque
orr mental materials, worth about the same as good qua turquoise
and the better jades (excluding imperial jad When it contains
light veins of other minerals, the value minishes, but not
excessively, as the effect is still vr pleasing.
Simulants and synthetics It was and is much
imitatr by glass, sometimes containing minute specks of metal
simulate pyrite, by stained chalcedony, and by a deep b sintered
aggregate of minute grains of synthetic spinel (plus the usual
metal fragments to simulate pyrite). A pr( uct has recently
appeared on the market which is e tremely homogeneous, very
deep blue with a violet tin and scattered with minute fragments
of pyrite. This called synthetic lapis lazuli, although it
does not corw spond exactly with the natural stone in chemical
compc tion. Furthermore, as the pyrite consists of grou fragments,
it never displays the characteristic crystal for The white
patches in low quality lapis lazuli are sometim colored blue
and this practice is not always easy to dete Natural stones
are sometimes impregnated with paraffin improve surface polish
and heighten the color. This is c same procedure often used
with poor quality turquoise, t the effects are not so far-reaching,
perhaps because la; lazuli is much less porous.
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