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Emerald
The name is of ancient origin. The Latin smaragdus
appears, in fact, to have referred to the stone we call em
ald, which is now considered as a distinct species. I: basically
the green variety of beryl, although not all gr quality green
beryls are called emeralds: yellow-gra stones are called heliodors;
soft blue-green or even F green specimens (their color due
to iron, not chromium in emerald) are called aquamarines.
Appearance The typical color
is a beautiful, distince hue known, in fact, as emerald green
and is due to tra of chromium in the crystal structure. But
emeralds car light or dark green, bright green or leaf green.
The vitrc luster is not outstanding, and is strongest in mediumstones
with few inclusions. All emerald contains Inclusi although
in the best quality stones, these are very faint not visible
to the naked eye. They show up under a ' 20x, or 40x lens.
The most common shape for gems > step or trap cut, which
is also known as the emeralr. They are occasionally given
a mixed, oval cut, whil: tique stones are found with hexagonal,
step cuts.
chon cuts, or pear shapes with a hole in them, often used
as pendants.
Distinctive features The typical emerald color is virtually
unmistakable. It is only equalled by some very rare specimens
of jadeite jade, which, however, is less transparent and has
different physical properties. To the initiated, the inclusions
in emerald can be highly distinctive: a bubble of gas in a
liquid (like a spirit level), within spindle-shaped or, more
rarely, truncated prismatic cavities; birefringent, circular
plates of mica; multifaceted pyrite crystals or calcite rhombohedra.
However, a microscope is almost always needed to recognize
them. Although not the typical emerald color, some green tourmalines
may look similar, but they can be distinguished either by
their marked pleochroism, or by the fact that tourmalines
which are given an emerald cut display alternating, longitudinal
lines of lighter or darker color, when viewed through the
table facet. Olivine may also be a verdant green color vaguely
similar to that of some atypical emeralds; but the powerfui
birefringence of olivine is detectable with a simple lens,
a double image of the opposite facet edges being clearly visible
in certain directions through the table facet. In an> case,
the density of either tourmaline or olivine immediately distinguishes
the stone from emerald.
Occurrence The biggest and
most beautiful emeralds come from the famous Chivor and Muzo
mines of Colombia. Much smaller quantities of emeralds, mostly
of medium-light color, come from Brazil, and small, very intensely
colored stones, characterized by numerous minute inclusions
of molybdenite with a metallic appearance are found in the
Transvaal.
In the last few decades, increasing quantities
of emeralds have been found in a series of small deposits
in Eas' Africa-principally in Zimbabwe, Zambia, and Tanzania
These are quite a strong color, sometimes with a bluishgreen
tinge; and they often contain mica plates and, sometimes,
thin crystal needles. The most famous of these emeralds are
the ones from Sandawana in Zimbabwe, which are valued for
their color. Emeralds with similar characteristics also come
from the mountains of India and Pakistan as well as the Soviet
Union (Urals), and formerly Austria Value Stones of fine color,
weighing more than 2 carats are among the most highly valued
gemstones, and their price may equal or exceed that of diamonds.
Less ideally colored varieties-too dark or too pale are worth
quite a lot less; and if they are slightly turbid as well,
the value i< reduced even further.
Simulants and synthetics The
Romans are known tc have imitated emerald with skilfully worked
green glass Glass was also used in later centuries, extraneou~
particles sometimes being incorpoeated to simulate inclusions.
Doublets have also been used as imitations,
with a lowe portion of green glass and a top portion of garnet,
or triF lets, with a layer of colored cement sandwiched betweer
two layers of colorless beryl, synthetic spinel, or quartz
Synthetic emeralds have likewise been widely produce over
the last few decades. Generally of good color, these are mainly
distinguished from the natural variety by the inclusions and
other growth features. There are a lot of these synthetic
stones about, but their cost is quite high, so that the market
for them is saturated.
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