More About Lab Rough Gemstones
What are rough gemstones?
Rough gemstones are uncut gems that are made up of crystalline structures and can be cut into desired shapes through faceting or cabbing and polished to reveal their lustre.
A gemstone in the rough is a raw gemstone that has not yet been cut or polished. Rough gemstones can be dull-looking, but can also be shiny with no reflection.
Natural gemstones are found in the rough when mined while synthetic gemstones that are grown in a laboratory are made into a rough form. In both cases, gemstones made or found in the rough offer manufacturers and factories the chance to maximise the surface area for cutting to create the ideal shape, while maintaining carat weight, clarity and colour. Dealers then sell these stones to manufacturers whose jewellery craftsmen would mount the faceted and polished gemstone according to designs by designers and create finished jewellery pieces, which are then supplied to jewellery brands and retailers.
Inter-Pacific provides meticulous cutting and polishing services to BIRON® Rough Stones that maximise light refraction and bring out the colour of the gemstones for the highest quality finish.
Varieties of Beryl: Emerald, Aquamarine, Morganite, Bixbite, and Heliodorl. Photo credit: Jeff Scovil/GEOLOGYIN
How are lab roughs grown?
Lab-grown roughs are uncut gemstones that are man-made in a controlled environment.
Different gemstones are made through different processes that replicate the same chemical compositions, optical and physical properties as their natural counterparts. Grown stones can be made through either the melt process or the solution process. Within each process, there is a wide range of methods to create uncut gemstones from a lab for sale.
In the melt process, the chemical composition remains the same throughout, from start to finish. Methods of this process include flame fusion or the Verneuil method, and the Czochrolaski method more commonly known as the crystal pulling method.
In the solution process, the resulting chemical composition differs from that of the start, but the chemical composition and other properties of the end result are the same as a gemstone’s natural counterpart. Methods of this process include flux melt and hydrothermal growth.
Flame-fusion synthetic sapphire crystals. Photo credit: Hrand Djevahirdjian(left), StoneSunberg(right)
How are rough gemstones cut and polished?
Rough gemstones are cut and polished through gem cutting which is covered by the term lapidary. The process is the same for both lab-grown and natural roughs. This involves a progression of abrasion by grit of harder substances, such as diamond, which holds a hardness level of Mohs 10. This is often used to cut and polish both gemstones and diamonds. Another common compound used is man-made silicon carbide grit of different sizes that holds a Mohs hardness of 9.5. These include sawing, grinding, sanding, polishing, drilling and tumbling.
Using these techniques, gemstones can be shaped into the following forms: cabochons, faceted stones, beads and spheres, inlays, intarsias and mosaics, cameos and intaglios, and sculptures.
A rock saw with a circular blade is used to cut into a rough gemstone. Water and oil are used to wash away debris and avoid overheating the saw blade or stone. The saw blade is usually made up of steel or copper, or a phosphor bronze, which is then impregnated with diamond grit along the outer edge for sawing.
Wheels are used to shape gemstones into a roughly desired shape known as a preform. This is done by using a silicon carbide or diamond-impregnated wheel, whereby oil and water are also applied to prevent overheating. Very coarse diamond or silicon carbide can rapidly remove the non-gem part of the stone, while finer grit is used for final shaping and sanding.
Fine grinding removes the scratches left on your stone from the wheel before. Photo credit: CABBING.COM
This uses even finer abrasive grit than grinding to remove scratches that might have been left behind from grinding. This is a slower process that allows for more control over the final shaping of a stone before polishing.
The creation of a mirror-like finish on a gemstone promotes ideal light refractory to bring out the brilliance of a gem. Small quantities of stone are removed through the process, which can involve fine grades of diamond alongside other polishing agents. For cabochons, felt, leather, cloth, wood, or cork can be used to create rounded surfaces.
This method is used by a gem cutter to create desired holes into gemstones, such as beads. This is done by using a diamond-tipped rod or tube that rotates into a gemstone.
Is used to smooth and polish larger quantities of rough gemstones, for example, to make beads. A rotating or vibratory tumbler can be used to wash stones with a combination of finer grades of abrasives and water over days or weeks.
Drilling gemstones. Photo credit: GEMCROWD
FAQs on Lab Created Rough
How to measure carats in lab rough gemstones?
A loose gemstone in the rough can be weighed as it is to get the carat size through converting from grams.
Cutting, faceting and polishing necessary for producing a finished cut stone will however mean that the carat weight of a cut stone will be lighter than the carat weight of the loose gemstone in rough from which it is made.
Are lab gems worth more cut or uncut?
An uncut synthetic gemstone in the rough is valuable in itself due to the transparent and humane supply chain from which it comes. Its light eco-footprint also adds to its value. A cut gemstone that is lab-grown is worth more because of the added costs of skilled labour used to expertly cut a gemstone. It is cut and faceted in such a way to refract the best amount of light, all while maintaining as much carat size as possible to be ready for use in jewellery pieces.
How to choose the right uncut lab gemstone?
To choose a top-quality rough gemstone that has not yet been cut, consider the colour saturation, shape and clarity. A unique colour or colour-play ability, such as found in opals, will show that the finished product will stand out after cutting and polishing. Shape and symmetry will determine whether it can be easily faceted or cabbed into the desired form that is easily mountable for its use, such as in jewellery.
A large rough gem may not yield many smaller pieces if it is irregularly shaped, meaning increased waste during gem cutting.
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