User:ChloejWard/Synthetic Gemstones

A synthetic gemstone is a lab recreation which typically shares the chemical composition and physical properties of a naturally existing mineral. There are mainly two categories for creation of these minerals, melt or solution processes.

Further, synthetic growth prevents the negative environmental effects associated with conventional mining for natural minerals.

Types of Synthetic Gemstones
Some gemstones are more difficult to synthesize than others and not all stones are commercially viable to attempt to synthesize. These are the most common on the market currently.

Synthetic Corundum
Includes ruby (red variation) and sapphire (other color variations) both of which are considered highly desired and valued. Ruby was the first gemstone to be synthesized by Auguste Verneuil with his development of the flame-fusion process in 1902. . Synthetic corundum continues to be made typically by flame-fusion as it is most cost-effective, but can also be produced through flux growth and hydrothermal growth.

Synthetic Beryls
The most common synthesized beryl is emerald (green). Yellow, red and blue beryls are possible but much more rare. Synthetic emerald became possible with the development of the flux growth process and is produced in this way and well as hydrothermal growth.

Synthetic Quartz
Types of synthetic quartz include citrine, rose quartz, and amethyst. Natural occurring quartz is not rare is synthetically produced as it has practical application outside of aesthetic purposes. Quartz generates an electrical current when under pressure and is used in watches, clocks, and oscillators.

Synthetic Spinel
Synthetic spinel was first produced by accident when can be created in any color making it popular to simulate various natural gemstones. It is created through flux growth and hydrothermal growth.

Creation process
There are mainly two categories for creation of these minerals, melt or solution processes.

Verneuil Flame Fusion Process (Melt Process)
Flame fusion process was the first process used which successfully created large quantities of synthetic gemstones to be sold on the market. This remains the most cost effective and common method of creating corundums today.

The flame fusion process is completed in a Verneuil furnace. The furnace consists of an inverted blowpipe burner which produces an extremely hot oxyhydrogen flame, a powder dispenser, and a ceramic pedestal. A chemical powder which corresponds to the desired gemstone is passed through this flames.This melts the ingredients which drop on to a plate and solidify into a crystal called a Boule. For corundum the flame must be 2000°C. This process takes hours and yields a crystal with the same properties as its natural counterpart.

To produce corundum, a pure aluminium powder is used with different additives to achieve different colors


 * Chromic oxide for ruby
 * Iron and titanium oxide for blue sapphire
 * Nickel oxide for yellow sapphire
 * Nickel, chromium and iron for orange sapphire
 * Manganese for pink sapphire
 * Copper for blue-green sapphire
 * Cobalt for dark blue sapphire

Czochralski Process (Melt Process)
In 1918 this process was developed by J. Czocharalski and is also referred to as the "crystal pulling" method. In this process, the required gemstone materials are added to a crucible. A seed stone is placed into the melt in the crucible crucible. As the gem begins to crystalize on the seed, the seed is pulled away and the gem continues to grow. This is used for corundum but is currently the least popular method

Flux Growth (Solution Process)
Flux growth process was the first process which was able to synthesize emerald. Flux growth begins with a crucible which can withstand high heat; either graphite or platinum which is filled with a molten liquid referred to as flux. The specific gem ingredients are added and dissolved in this fluid and recrystallize to form the desired gemstone.This is a longer process compared to the flame fusion process and can take two months up to a year depending on the desired final size.

Hydrothermal Growth (Solution Process)
Hydrothermal growth process attempts to imitate the natural growth process of minerals. The required gem materials are sealed in a container of water and placed extreme pressure. The water is heated beyond its boiling point which allows normally insoluble materials to dissolve. As more material cannot be added once the container is sealed, in order to create a larger gem the process would begin with a "seed" stone from a previous batch which the new material will crystalize on. This process takes a few weeks to complete.

Characteristics
Synthetic gemstones share chemical and physical properties with natural gemstones but there are some slight differences that can be used to discern synthetic from real. These differences are slight and often require microscopy as a tool to distinguish differences. Undetectable synthetics pose a threat to the market if they are able to be sold as real rare gemstones. Because of this there are certain characteristic gemologists look for. Each crystal is characteristic to the environment and growth process under which it was created.

Gemstones created from the flame-fusion process may have


 * small air bubbles which were trapped inside the boule during formation process


 * visible banding from formation of the boule
 * chatter marks which on the surface which appear crack like which are caused from damage during polishing of the gemstone

Gemstones created from flux melt process may have


 * small cavities which are filled with flux solution
 * inclusions in the gemstone from crucible used

Gemstones created from hydrothermal growth may have


 * inclusions from container used

History
Prior to development of synthesising processes the alternatives on the market to natural gemstones were imitations or fake. It was in 1837 that the first successful synthesis of ruby occured. French chemist Marc Gaudin managed to produce small crystals of ruby from melting together potassium aluminium sulphate and potassium chromate through what would later be know as the flux melt process. Following this, another french chemist Fremy was able to grow large quantities of small ruby crystals using a lead flux.

A few years later an alternative to flux melt was developed which led to the introduction of what was labeled "reconstructed ruby" to the market. Reconstructed ruby was sold as a process which produced larger rubies from melting together bits of natural ruby. In later attempts to recreate this process it was found to not be possible and is believed reconstructed rubies were most likely created using a multi-step method of melting of ruby powder.

Auguste Verneuil a student of Fremy went on to develop flame-fusion as an alternative to the flux-melt method. He developed large furnaces which were able to produce large quantities of corundums more efficiently and shifted the gemstone market dramatically. This process is still used today and the furnaces have not changed much from the original design. World production of corundum using this method reaches 1000 million carats a year