Synthetic Gemstones: Varieties and Composition
Synthetic gemstones are made in the laboratory but virtually share all the composition, chemical and physical properties of its natural counterpart. Synthetic gemstones have been manufactured since the 1800s. There are strict guidelines for synthetic gemstones on how they are marketed and sold.
Lab Created Loose Gemstones
Chatham is recognized as a superior lab-created loose gemstone. There are a large variety of loose synthetic gemstones such as rubies, blue, pink and white sapphires, and emeralds.
Lab-created gemstones are real stones but are created synthetically. The methods used to create these synthetic loose gemstones require expensive equipment and the process is energy-intensive. Though these aren’t as valuable as natural gemstones are, but synthetic or lab-created gemstones have the same chemical and physical properties.
Lab Created Corundum
Corundum is extremely hard crystallized material used as an abrasive. Ruby and Sapphire are varieties of corundum. Synthetic corundum is available at many price levels. Ruby became the first gemstone to be created as a synthetic stone.
- Hexagonal crystal structure
- An extremely hard crystalline compound
- Excellent Abrasive
- Tough, hard, and chemically stable
Chemical Composition: Al2O3
Color: Traces of various metals produce colors, such as red for ruby and blue for a sapphire.
Diaphaneity: transparent to translucent
Hardness: nine on the Mohs scale
Specific Gravity: 3.9 to 4.1
Crystal System: Hexagonal
Uses: To make industrial bearings, scratch-resistant windows, and many other products.
Lab grown diamonds are pure crystallized carbon diamonds grown or created in a laboratory. They have the same properties as of a naturally occurring diamond; the only difference is that the former are lab-created. These are graded on the same scale as of the natural diamonds. They are essentially carbon compounds, grown in a controlled laboratory environment.
Chemical vapor disposition is a process that releases carbon atoms that precipitate to form grown diamonds due to a chemical reaction in a vacuum chamber.
High-pressure and high-temperature (HPHT) growth occurs at a pressure roughly equivalent to the pressure exerted by the commercial jet plane. The temperature used is around 1300-1600 degrees Celsius.
A carbon source such as graphite or diamond powder is kept in a chamber with other compounds to ease the diamond growth above a diamond seed.
- High-thermal conductivity
- High Refractive index
- Fairly high dispersion
- Diamonds are the hardest known materials. Hardness depends upon its purity and orientation.
Toughness: 7.5–10 MPa·m1/2
Yield Strength: 130–140 GPa
Tensile stress: ∼89 to 98 GPa
Conductivity: Most diamonds are insulators while some are semi-conductors as well.
Surface Property: Diamonds are naturally lipophilic and hydrophobic, which means the diamonds can be easily wet and stuck by oil.
Synthetic Processes to create gemstones:
- Flame Fusion: The process necessitates powdered chemicals on a high-temperature flame, where it melts to form a synthetic crystal. It is today used as an inexpensive method to make gemstones such as corundum.
- Crystal Pulling: The compounds are melted and synthetic gems are created from seed that is dipped into melt and slowly drawn away as it grows.
- Flux Growth: is a solution process which uses a flux that together with other compounds acts like water, dissolving other compounds well in it. With the gradual cooling of the synthetic materials, it results in the synthetic crystals. This process requires patience and significant investment.