Loose Emeralds are the grass green variety of the gemstone called beryl.
Although all Emeralds are beryl, not all beryls are emerald (see Beryl).
Emeralds - Coloration
Pure beryl is colorless, often called white, and although quite rare, tends not to be valuable
because it does not have much brilliance. Colors, as in many gemstones, are caused by
small amounts of impurity, usually metallic oxides. This is a another case where
impurity is desirable.
Chromium, in the form of chromic oxide, causes the bright grassy green coloring in beryl,
thereby producing Emeralds. Vanadium can also affect the exact shade, as may
traces of iron. It is also possible to have green beryl which is not Emerald,
because the coloring agent is not chromium.
Emeralds - Durability
Emerald, along with other beryls, is quite hard, having a hardness of 71/2 to 8 on
Moh's scale, compared with 10 for diamond, 9 for corundum, and 8 for topaz. Hardness is
generally a desirable feature in gemstones because it relates directly to durability.
Emeralds - Sources
The earliest known source of Emerald was near the Red Sea in Egypt, the so-called
Cleopatra's Emerald mines. They were probably worked from about 2000 B.C.,
apparently the location of them was lost in the middle ages, and not rediscovered until 1818.
Most Emeralds used in ancient jewelry are believed to have come from these mines.
They are not currently worked because of the low quality of crystals found.
Emeralds have been found in Austria since Roman times, in the Legbach ravine at
Habachtal near Salzburg. These are no longer commercially mined.
Columbia is generally recognised as the source of the world's finest quality Emeralds,
both in the past and the present. The Columbian Indians were using them before 1537,
when Quesada conquered Columbia. Later the Spanish discovered that the Emerald
mines were at Somondoco, which means "god of the green stones", and which is now known as
Chivor. The best colored Columbian Emeralds are said to be those from the Muzo
mine, although another mine at Cosquez is also highly rated.
Russia has been another important source of Emeralds in the past. Most Russian
Emeralds coming from Sverdlovsk or Ekaterinburg in the Ural Mountains.
Emeralds were discovered in Australia in 1890 in New South Wales. They were
discovered between 1927 and 1929 at Gravelotte in South Africa, followed by other sources.
Another important source of superb quality Emeralds, usually only of small size,
is Sandawana in Zimbabwe formerly Southern Rhodesia. These were discovered only in 1956.
Emeralds were known in India from antiquity, but their source is not certain.
The earliest known Indian source was 1929 at Arawalli in Rajahstan, other sources being
discovered since. The quality of Indian emeralds is very variable, but most are
of lower quality which are often polished as beads.
Other sources of Emerald include Norway, North Carolina, Connecticut, Maine,
New Hampshire, although non of these are very important.
Emeralds - Pricing
The price range of loose emeralds is very large, ranging from under a few dollars per carat
to many thousands of dollars per carat, depending primarily on color, but also on brilliance
and clarity. Large, brilliant clear emeralds are very rare and expensive, in fact any clear
emerald is quite scarce, regardless of size.
Many people have the opinion that the darker the Emerald . . . the better, just as
many seem to believe the opposite. Neither of these opinions is correct.
A very dark Emerald would appear black, and would not be very attractive or desirable. The
darkness often being caused by inclusions. An extremely pale emerald would be colorless, and
not particularly attractive or valuable. The truth lies between the two extremes. The most
desirable emeralds are generally those with an intense grassy green color, with obvious
sparkle and life, and free of any inclusions. Some experts say that a dark velvety green is
the most valuable. Ultimately which is "best" is a subjective matter, and personal preference
is important. Our usual advice to potential customers is to buy whichever color of emerald
they personally find the most attractive. We also think it's slightly sad that we need to give
this advice. Buy what you like, using your own judgment, rather than allowing yourself to be a
slave to fashion and buying what you think will impress other people.
The main choice in the color of emeralds depends largely whether you prefer lighter but
brighter stones, or a deeper more intense color.
Emeralds - Treatment
The vast majority of emeralds are oiled, that is to say, immersed in oil which fills the many
cracks and fissures to which emerald is prone. This has the effect of reducing the visibility
of the inclusions, and improving the clarity of the stone. Sometimes oiling also improves the
color. Green colored oil is sometimes used to enhance the stones natural color, there are also
other fillers used which are more permanent than oil.
Because oil filling of emeralds has become almost universal, it is generally not considered
essential to disclose this fact. We suggest that anyone wishing to buy a high quality or
expensive emerald should request a gemstone laboratory certificate stating that the stone is
natural and not oiled, but be prepared to pay extra for a certificated stone. Most modern
emeralds are likely to be oiled at the mines, and again at the cutters.
Technical Characteristics
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Chemical Composition:
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Be3Al2(SiO3)6 - Beryllium Aluminium Silicate
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Hardness:
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7.5 - 8
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Specific Gravity:
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2.65 to 2.76
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Refractive Index (R.I.):
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1.560 - 1.565 to 1.587 to 1.593
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Bi-refringence:
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0.005 to 0.009
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Optic Sign:
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Negative
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Optical Character:
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Uniaxial
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Crystal Structure:
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Hexagonal
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