(via Gemmology Queensland, Vol 3, No.1, Jan 2002/IGC Conference Madrid 2001) Vladimir S Balitsky writes:
Synthetic gems
In modern Russia in industrial scales practically all kinds and varieties of synthetic analogues of natural gems are produced as well as it was in former USSR. Moreover, crystals of the whole row of compounds having no analogues in nature but possessing properties of gems are synthesized. A list of all synthetic gems produced at present in Russia is given in Table 1 with methods of their obtaining approximate volumes of production and their prices. As can be seen, leuco-sapphire, ruby and sapphires are produced in large quantities. They are grown mainly from the melt by the methods of Verneuil, Czochralski, Kyropulus and Zone melting. Lately they have been grown in small quantities by hydrothermal and flux methods. Traditional Russian synthetic gems also include quartz and its colored varieties especially amethyst, citrine, blue and green quartz. Lately they have developed new technologies of producing two colored amethyst-citrine quartz (ametrine), pink transparent phosphorous-bearing quartz and unusual copper-bearing aventurine in small quantities. Under artificial conditions drusses of both colorless and colored quartz are also grown.
Table 1
Synthetic gems produced in Russia at present
Name: Alexandrite
Growth technique: Czochralski
Approximate production/kg per year: up to one hundred
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Alexandrite
Growth technique: Flux
Approximate production/kg per year: a few kg’s
Approximate price of raw material (US$/per kg): 1000 – 7500
Name: Amethyst
Growth technique: Hydrothermal
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 50 – 150
Name: Ametrine
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundred
Approximate price of raw material (US$/per kg): 100 - 150
Name: Aquamarine
Growth technique: Hydrothermal/Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 5000
Name: Cubic Zirconium Oxide (CZ)
Growth technique: Skull Melting
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 30 – 60
Name: Diamond
Growth technique: HPHT
Approximate production/kg per year: up to 2
Approximate price of raw material (US$/per kg): 1000000
Name: Emerald
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: up to 50
Approximate price of raw material (US$/per kg): 5000 – 7500
Name: Emerald Drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 1000 – 15000
Name: Forsterite
Growth technique: Czochralski
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000
Name: Gadolium Gallium Garnet (GGG)
Growth technique: Czochralski
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 10000
Name: Leuco sapphire
Growth technique: Czochralski
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Vernueil
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 250 – 300
Name: Leuco sapphire
Growth technique: Kyropulus
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 350 - 400
Name: Leuco sapphire
Growth technique: Horizontal Zoning Melt
Approximate production/kg per year: a few thousand
Approximate price of raw material (US$/per kg): 400 – 500
Name: Morganite
Growth technique: Hydrothermal / Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 3000 – 7000
Name: Malachite
Growth technique: Chemical precipitation from aqueous solutions
Approximate production/kg per year: up to thousand
Approximate price of raw material (US$/per kg): 40 -70
Name: Moissanite
Growth technique: High pressure sublimation
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 25000 – 50000
Name: Opal noble
Growth technique: Chemical precipitation + impregnation by plastic or zirconium hydroxide or silica + high temperature treatment
Approximate production/kg per year: a few dozen
Approximate price of raw material (US$/per kg): 20000 – 35000
Name: Quartz colorless
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 600
Name: Quartz colored (yellow, green, blue, brown, smoky, milky)
Growth technique: Hydrothermal
Approximate production/kg per year: a few hundreds of thousands
Approximate price of raw material (US$/per kg): 40 – 80
Name: Quartz pink (transparent)
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 3000 - 5000
Name: Quartz drusses
Growth technique: Hydrothermal
Approximate production/kg per year: a few dozens
Approximate price of raw material (US$/per kg): 50 – 100
Name: Ruby
Growth technique: Vernueil / Czochralski / Horizontal Zoning Melt
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Ruby
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 - 10000
Name: Sapphire
Growth technique: Verneuil / Czochralski
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 250 – 1000
Name: Sapphire
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 5000 – 10000
Name: Spinel
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Spinel drusses
Growth technique: Flux
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 25000
Name: Turquoise
Growth technique: Chemical precipitation + high pressure treatment
Approximate production/kg per year: a few hundreds
Approximate price of raw material (US$/per kg): 50 – 80
Name: Yttrium Aluminum Garnet (YAG) (Colorless and colored)
Growth technique: Czochralski / Horizontal Zone Melting
Approximate production/kg per year: a few thousands
Approximate price of raw material (US$/per kg): 400 – 700
Name: Zincate
Growth technique: Hydrothermal
Approximate production/kg per year: a few
Approximate price of raw material (US$/per kg): 30000
An essential role in the production of synthetic gems in modern Russia belongs to emerald. It is mainly grown under hydrothermal conditions, but in small quantities it is obtained from flux. Besides emerald, other colored varieties of beryl are grown in very limited quantities. Among other popular synthetic gems grown in Russia, one should notice alexandrite and spinel. First, it was grown by Czochralski and flux methods, and then by Verneuil and flux. The most precious of them are crystals grown from flux. Among other synthetic gems, refined black and white noble opal is also produced. The material may look very similar to the natural opal. Synthetic malachite has also been produced successfully. A considerable progress has been made in the synthesis of large diamonds (yellow, blue and colorless) with the maximum weight up to 5 ct. Within the last two years synthetic moissanite has also been produced. However both synthetic diamonds and synthetic moissanites are produced in rather restricted quantities.
Enhanced gems
Many gems found and imported into Russia (corundum, topaz, quartz, garnet, danburite, scapolite, beryl, tourmaline, turquoise, coral, charoite, lazurite, agates etc.) are of low quality. The gems are often subjected to enhancement with the purpose of increasing their quality. Table 2 gives a list of stones with indicative treatments.
Name: Agate (chalcedony)
Enhancement process: impregnation / heat treatment / irradiation
Enhancement effect: pale colors to yellow, brown, green, blue, black and red; pale colors to brown and red; change of color to dark gray.
Name: Amazonite
Enhancement process: heat treatment / dyeing
Enhancement effect: improvement of color
Name: Amber
Enhancement process: reconstruction / heat treatment / pressing
Enhancement effect: augmentation of weight; improvement of inner structure with induced cracking; augmentation of weight
Name: Charoite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Corundum (colorless and colored)
Enhancement process: heat treatment / heat treatment with diffusion / surface coating
Enhancement effect: colorless and pale colors to blue
Name: Danburite
Enhancement process: irradiation / heat treatment
Enhancement effect: remove colorless to brownish—pink / fading
Name: Heliodor
Enhancement process: heat treatment
Enhancement effect: remove yellow to blue (aquamarine)
Name: Lazurite
Enhancement process: impregnation / heat treatment
Enhancement effect: improvement of color
Name: Nephrite
Enhancement process: hydrothermal treatment / irradiation
Enhancement effect: lightening of dark green color to white / darkening of green and brown to black
Name: Quartz
Enhancement process: heat treatment / irradiation / surface coating
Enhancement effect: dark smoky to pale smoky or greenish yellow or colorless / colorless and pale colors to smoky or greenish yellow / colorless and pale colors to pink or blue
Name: Radonite
Enhancement process: dyeing
Enhancement effect: improvement of color
Name: Topaz
Enhancement process: irradiation / irradiation + heat treatment
Enhancement effect: colorless and pale colors to yellow brown or reddish brown / colorless or brown to brownish green or blue / brown or orange to pink / brown or green or blue to colorless
Name: Turquoise
Enhancement process: impregnation under high temperature and high pressure
Enhancement effect: improvement of color / rise of hardness
No comments:
Post a Comment