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.Isuppose it could be reasoned that if you couldn t make money-creating emer-alds, at least you could make money repairing their fractures.) In this processberyllium and aluminum oxides (with lithium chromate as the coloring agent)were placed in the bottom of a crucible as the nutrient.The crucible was filledwith lithium molybdate, and seed crystals were attached to the upper partof the crucible, beneath a platinum baffle.Quartz plates (which supply theSiO2) were placed above the baffle.The material was heated to 800%Cduringthe growth process.At the end of World War II, the costly platinum apparatuswas destroyed and never replaced.During the1920s, Richard Nacken of Frankfurt, Germany, was also grow-ing small emeralds using a flux process, but his methods were not revealeduntil 1978.This secretiveness was characteristic of most early synthesizers.Aneven better technology called  flux growth was developed in the 1950s.Thetechnique was first applied to rubies (which are commercially more importantthan emeralds).In general, synthetic emeralds are created by one of two methods or avariant thereof: flux growth and hydrothermic.Most synthetic companies useboth processes at various times, although they may favor one or the other.The details of making synthetic emeralds are not publicly discussed, andimprovements are constantly being made.The hydrothermal process is one that duplicates the underground condi-tions that give birth to Colombian emeralds.The first such emeralds were 166 From Satan s Crown to the Holy Grailproduced by Johann Lechleitner in Innsbruck, Austria, toward the end ofthe 1950s.This method transforms low-grade melted beryl (the  nutrient )around a solid beryl  seed in a hydrothermal environment.Color inducingchemicals, such as vanadium and chromium are melted along with it.Thehydrothermic process starts by gradually heating the autoclave.Subsequentrise in temperature leads to rise in pressure, as a result of liquid expansioninside the inner vessel.Once the temperature rises to about 600%C and pressure is around 800PSI, the process reaches an ultimate equilibrium and a melt process begins.The seed attracts smaller particles of the same origin and the growth processbegins, depositing layer upon layer on itself like pearl, resulting in undulatedgrowth lines in hydrothermally grown gems.The process takes about fourweeks.However, if the process is slowed down, the  layers are depositedmore slowly, resulting in growth lines being less clearly defined (more difficultto detect).Most hydrothermically grown emeralds have the following features:Refractive index: 1.571 to 1.578 D.R -.007Specific gravity: 2.678Clean color with constants close to those of a naturalPronounced red fluorescence under both SW and LW UV lightRed glow can even be seen under strong white lightBright red under Chelsea filterNail-like inclusions with the head being phenakite crystalsHydrothermally grown synthetic emeralds were once manufactured by UnionCarbide (1965 1970) as Linde-Created Emeralds.Linde was a division ofUnion Carbide.Other manufacturers who have used this method or a variantof it include:The Regency Synthetic Emerald (Vacuum Ventures) is created using theoriginal Linde technique and Union Carbide patents.Its properties are quiteclose to those of the natural stone, although the specific gravity is somewhatlower, at 2.68.This stone contains very little iron, so it has a high SW UVtransmission factor and a strong red fluorescence (even under a beam ofhigh-intensity white light).These stones often have wedge-shaped, daggerlikegrowth tubes, two-phase features stemming from phenakite crystals, andsometimes a  healed crack feature.They can even contain fluid inclusionbut lack the alkalis that one would expect to find in a natural emerald.The Lechleitner hydrothermal method, a process developed in several stagesover many seed plates of synthetic emerald (as with yogurt, you often needto have some emerald to make some more emerald) were placed over andover into an autoclave, thus growing several layers of emerald plate.Crystals Fake Emeralds and Their Kin 167were then cut.Between the different growth phases, poorly colored or impurecrystals were removed.The necessary apparatus is quite similar to the oneused in early flux products.Most details of the process are kept secret, but Lechleitner synthetic emer-alds have the following features:Refractive index: 1.575 to 1.581Specific gravity: 2.69Inclusions not common to emeraldNetwork surface of cracksAnother synthetic emerald producer using the hydrothermic method isTairus Created Gems.The company had its roots in the late 1960s, whena group of young Russian scientists working on a top-secret project at theSiberian Branch of the Russian Academy of Sciences to develop a perfectconductor for a guided laser beam, produced some fine emerald crystals us-ing both hydrothermal and flux processes.Two years later they were orderedto stop, and they never again heard from the authorities who ordered theseexperiments.But they still had the rocks.The stones were very similar to thebest emeralds from the Ural Mountains, and ranged in color from dark blueto bright yellow.The Russians had been more interested in technology thanin gems, but were smart enough not to pass up a good thing [ Pobierz całość w formacie PDF ]