Different Amethyst TreatmentBy:Yuman Hussain Summary: Different Amethyst treatment tells about different laboratory treatments of Amethyst including heat treatment and irradiation process and its effect including its commercial value.
Different Amethyst Treatment, its Effect and respective Commercial Value
Amethyst has been the most sought after stone from time immemorial. It was
the favorite stone of British monarchy and sparkled in the crown of
Catherine the Great and ancient Egyptian royals. Amethyst being birth stone
for the month of February is the common quartz used in jewelry. The healing
and magical properties of Amethyst made it valuable right from the middle
Ages. Amethyst was considered symbol of celibacy and piety by the Christian
Priests in the western countries. Considered as a strong antidote against
drunkenness it literally meant 'not to intoxicate' in ancient Greece. Violet
and Purple varieties of Amethyst are considered as symbol of heaven, as they
are related to the constellations of Pisces and Aries.
Amethyst is transparent quartz having the presence of manganese, which
produces the stunning purple color. It also has iron content which adds
variation to the colors. Its brilliant color is therefore often compared
with most expensive gemstones. Generally cut in a six sided prismatic
crystal shape it produces a sparkling cluster. Amethyst are available in
wide range of sizes, shapes and colors from deep purple which are considered
valuable particularly a rich purple with rose flashes to pale colors like
Lilac.
This hard and versatile stone is available world wide however different
regions produce their own unique varieties. Most of these stones are mined
in Latin American countries like Brazil, Uruguay, Argentina and Bolivia as
well as in some African countries like Zambia and Namibia. The stones from
the mines of South America are usually larger in size but the African stones
are considered better in color and saturation. Some dark colored small sized
amethysts are mined in Australia also. These stones are graded according to
clarity and color. The Siberian stones belong to higher grade outclass all
other competitors in richness and depth of their violet and purple hues.
Uruguay mines produce medium grade stone having properties of medium to dark
tone and moderate to strong saturation. The lower grade Amethyst in light to
medium color is found in Brazil.
To enhance the beauty many gemstones
are treated to various processes since antiquity. These human initiated
processes are basically done to improve the nature and color of the stones.
These are usually undetectable and somewhat irreversible processes. The two
main processes are heat treatment and irradiation which if done properly can
dramatically change the Amethyst's clarity.
Heating
Heating is the most common treatment which can alter the color of a stone
to lighten, darken, or change completely. Very dark amethyst is heated to
produce lighter shades. Most of the amethyst available in the gem market is
enhanced to get exotic shades. On treating Amethyst under controlled
conditions one can produce some very astonishing colors or intensify the
royal purple color at 400c to 600c. This heat treatment causes inclusions to
expand causing tiny fractures in the crystal surrounding them. It is a
permanent and common Amethyst treatment and last forever. Most of the large
darker stones exhibiting color zoning are often heat-treated to produce
dramatic color changes.
Citrine from Amethyst
Citrine, yellow colored quartz though occurs naturally is produced by
heating amethyst with the proper iron content under controlled conditions.
It was discovered long ago that by heat-treating light colored amethyst or
smoky quartz a small percentage would turn into attractive golden yellow
color. The only difference between amethyst and citrine is the oxidation
state of the iron impurities present in the quartz. When heated, the iron
impurities are reduced to make amethyst's purple color to fade and turn
yellow to reddish-orange (citrine).
This process depends on various factors including the percentage of the iron
impurities present and the heating duration and time. Much of citrine which
comes from Brazil is heat-treated. Some unusual like golden orange or Rio
Grande citrine or dark sherry colored or Madeira citrine are highly prized.
On subsequent heating amethyst looses color and turns grey or white making
it worthless.
Vermarine or Prasiolite
There is green quartz called 'Greened' amethyst or Vermarine also known
as Prasiolite having light to medium color. It is produced by careful
heating of Brazilian amethyst. A collector's item though inexpensive is not
available easily. The heat treatment of Amethyst between 878 and 1382
degrees F may produce light yellow, red, brown, green or colorless varieties
of stones. The result of heat treating these gems are stable so they hardly
require any special care while wearing .But they should not be steam-cleaned
due to their susceptibility to heat.
Irradiation
Sometimes irradiation an uncommon treatment is used to get unusual colors
like clear green or dark/black smoky quartz. This process involves
penetrating material with subatomic Gamma rays. These rays invade the
electrons of the gems making them lose and captured by other atoms. It
changes the light absorbing pattern and hence the change in the color. In
the irradiated quartz crystal the color distribution would be more at the
terminations and less at the roof. Through this process Amethyst can get its
original purple color from the yellow citrine which re-oxidizes the iron
impurities. This irradiation occurs either by synthetic means in the lab, or
through natural radioactive decaying of minerals present in close vicinity.
In most cases this is a reversible process. But excessive heat can change
the distribution of the iron impurities within the quartz making it
impossible to convert it back to amethyst.
Though considered at par with precious gemstones like
Diamond,
Sapphire,
Ruby and
Emerald , Amethyst has lost much of
its value due to easy availability and discovery of vast deposits in some
Latin American countries like Brazil. Earlier Amethyst was a prized
possession due to its scarcity. In the recent years the technological
advancements have led to its wide spread imitation in the labs making it the
most market friendly stone.
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