Different Amethyst Treatment
by Yuman Hussain
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 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.
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.