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Polishing pretty stories: Engage customers with the entire tale of coloured stones

By Diana Jarrett

93.77-carat colour-change Csarite (diaspore) cut by Rudi Wobito.
Photo courtesy Wobito Gems

Coloured gems sell—we don’t even need to classify them as ‘precious’ and ‘semi-precious’ anymore. Depending on a stone’s provenance and rarity of colour and size, today’s shoppers are willing to dig deep into their pockets and shell out serious money for many rainbow-hued gemstones. Lesser known but highly collectable jewels like taaffeite, alexandrite, and red beryl have jewellery buyers considering five-figure price tags, just for starters.

Retailers are getting savvier about conveying the stories about gemstones as a sales tool to entice clients. This is valid, of course. Once collectors understand the origin of their favourite stone, a deeper appreciation develops, and they become even more eager to collect. In most cases, coloured gems are sourced from exotic locales the consumer will never visit in person. Occasionally, the shopper has never even heard of the place (where is Kazakhstan anyway?).

Tell the whole story

Rough gems on the dop and faceted by Mike Soebbing.
Photos courtesy Mike Soebbing/The Gemstone Man LLC

Key to conveying a coloured gemstone’s worth is educating the consumer on cutting challenges, along with cutters’ preferences. Greater awareness of what a stone goes through before being purchased aids the client’s grasp of its intrinsic value, which is a clarifying moment. Indeed, when you educate a shopper about the scarcity of a stone, the difficulty in acquiring it, and the challenges faced when polishing it, the client develops an increased understanding of its retail price.

The nature of the species informs a cutter of what to expect when they place a gemstone on the wheel. As natural minerals, gems develop in their own unique way, giving crystals distinct cleavage and fracture characteristics. Cutters working with these constraints produce jewels that retain weight while also displaying optimal colours. Knowledge of the crystal’s axes informs the cutter of which direction to shape the stone. An iolite, for example, can appear like a Tanzanite twin when cut in a certain direction, while shaping it along a different axis may result in something looking more like smoky quartz.

Professional stone cutters often become known for polishing specific gems. Whether this is due to their expertise in handling difficult crystals or simply because they love a certain jewel, many revert to cutting the same type over and over. Learning from experienced cutters provides unexpected insight into the process of transforming rough pebbles into the dazzling gemstones collectors crave.

Childhood dream

Namibia-based gem cutter Clara Venter traces her fascination with gemstones to her early years.

8.45-carat Namibian orange tourmaline by Clara Venter, Royal Art Faceting.
Photo courtesy Royal Art Faceting

“My dad used to work for a local gem dealer,” she explains. “When I was about 13 years old, I saw a rough piece of tourmaline for the first time in my life. When the old man showed me what it looked like after cutting, I was amazed by its transformation. Right there, I decided, one day, to become a gem cutter, and many years later it happened.”

Interestingly, Venter says tourmaline is by far the most challenging gemstone for her to cut.

“I have cut hundreds of tourmalines over the years, and some can be very easy and satisfying,” she says. “Then, you have those that develop stress fractures. These can be quite challenging, especially when the rough was given by a client to cut.”

The problem, Venter explains, is “people don’t understand some gems can develop these stress fractures.” As such, tourmaline—a species she loves—is the one she has rejected most often.

“Over time you learn to identify which piece of rough will crack on you,” Venter says. “Sometimes, it’s the most beautiful one you have to say ‘no’ to.”

Venter’s personal favourite to work with, though, is demantoid garnet, which she feels doesn’t get enough credit.

“Whether you’re a novice cutter or very experienced, [these gems] will never disappoint when it comes to producing their brilliance.”

Of course, every cutter has at least one completely unforgettable stone. For Venter, it was a client’s 24.25-carat Lagoon coloured tourmaline.

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“I created a design especially for the rough, and it turned out amazing,” she says. “That gem was bought by a collector in the United States, and I guess it’s living the American dream now.”

Homegrown exotics

An example of Montana sapphire’s beautiful bi-colour by Kory Pettman, owner of Texas-based Kory Pettman Gems.
Photo courtesy Kory Pettman

Kory Pettman, owner of Texas-based Kory Pettman Gems, is recognized for her expert cutting of Montana sapphires. The western U.S. region is home to some of the largest sapphire deposits in the world.

“I can visualize the gold miners in 1865, some 14 miles from Helena at the Eldorado Bar on the Missouri River, finding these strange crystals clogging up their sluice boxes,” Pettman says.

These ethically sourced sparklers were first considered a nuisance until gold miner Ed Collins, “recognized their value and took them to Helena, where they were identified as sapphire,” Pettman explains.

“There are some wonderful bi-colours, particularly heat-treated material from Dry Cottonwood Creek,” she continues. “When well faceted, the high-clarity Montana sapphires possess a great brilliance and occur in every colour of the rainbow.”

A bonus, Pettman says, are rare and illusive Montana rubies. Of course, these homegrown beauties are not without some caveats, she says. Namely, finding large, clean rough is a major challenge.

“Ninety-five per cent of Rock Creek sapphire rough ranges in size from two to five millimetres,” Pettman says. “The majority are less than four millimetres. Sapphires weighing two carats are rare. Clean, faceted Montana sapphires larger than three carats are extremely rare.”

Consumers may not know much about Montana sapphires, but discovering their details adds another layer of appreciation for the stones.

“Due to their unique chemistry, some Montana sapphires exhibit a colour change when the viewing environment changes from fluorescent (or daylight) to incandescent light,” Pettman explains, adding her favourite colour-change sapphires go from green to purple.

Beware of fractures

Forty-year veteran lapidarist Mike Soebbing, founder of The Gemstone Man LLC, tackles restoration jobs and precision gemstone faceting for his loyal clientele. After many decades, one stone remains a challenge to perfect.

Sunstone from Suncrystal Mining.
Photo courtesy Mike Soebbing/The Gemstone Man LLC

“By far,” Soebbing says, “the most difficult stone has been spodumene, or Kunzite. Due to its perfect cleavage, it will cleave or fracture unpredictably at any time during cutting or polishing.”

These ‘problem children’ of the gemstone variety cause Soebbing to decline some Kunzite jobs.

“It’s something I rarely, if ever, do with any other species,” he says.

While gemstones such as these may border on unmanageable, Soebbing says other crystals are downright captivating.

“Specifically, trichroic sunstone specimens are the most fascinating,” he says. “Depending on the orientation of the rough, they can produce brilliant colours or muddy brown messes. They are a terrific challenge and each one is different. Working with sunstone is a special challenge I enjoy very much.”

Soebbing adds certain polishing memories will remain with him forever.

“My sister, a true rockhound, purchased a rough Herkimer diamond at Tucson in 2018,” he says. “We shared a love for gemstones in different ways. She collected beads and crystals, creating beautiful mosaics. She, very tongue-in-cheek, asked if I knew of anyone who cut gemstones when she was well into her battle with cancer. I was lucky enough to cut that Herkimer for her before she passed in 2019. Thankfully, she got to appreciate it.” 

Expert in emerald

Some cutters specialize exclusively in gemstones from their homeland—like Jaime Quintero, who has 25 years of experience cutting in the emerald district in Bogota, Colombia. Not every gem cutter is proficient at polishing emerald crystals, Quintero notes. Inclusions specific to emeralds determine how the gem can be shaped.

“Colombian emeralds are unique,” he says. “They take on gas, liquids, and crystals in the crystallization process while in the mine, creating complex branch-like inclusions called Jardin or garden.”

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The dicey part of cutting concerns those tiny internal fractures, Quintero says.

Jaime Quintero polishes emeralds in Bogota, Colombia.
Photos courtesy Jaime Quintero

“These make the cutting process very tricky,” he continues. “We must work around the fractures, trying to keep them far from the surface of the emerald, [being sure] not to touch them in any way so as to risk breaking down the entire gem, even on the polishing disk.”

Colour is king

When it comes to emeralds, it’s all about the transparent green colour. Only expert cutters with years of experience can determine the ideal way to cut the stone with an eye for colour zoning.

“Some emeralds do present colour zoning, so their green hue may not be consistent throughout the entire crystal,” Quintero says.

There are, however, ways to get around this.

“We need to identify where the deepest green is inside the crystal and orient it in the centre of the shape we are creating,” he explains. “Otherwise, the emerald will show different green tones—some dark green and others light.”

In some instances, despite a cutter’s best efforts, it is unavoidable for emerald inclusions to reach the surface. What then?

“They are inevitable,” Quintero says. “This is when we must make an important decision: should we buff out the pit and try to get rid of it?”

Unfortunately, however, the value of emerald is in its carat weight. Further still, the cutter cannot always determine how deep a pit goes inside the stone. With microscopic features, one cannot always be sure of their layout inside the gem.

“Every time the emerald goes over a polishing disk, we lose money,” Quintero says.

“You repolish the emerald and get rid of the superficial pit,” he cautions, “or you can make it bigger.”

After decades in the business, Quintero has plenty of stories. 

“A dealer of loose emeralds once bought a ‘ganga’—an inexpensive specimen rock from the inside of the mine, containing pieces of low-grade emerald, pyrite, and quartz,” he says. “You often find them in the emerald district in various sizes and shapes sold as souvenirs, ranging in price from $20 to $500.”

“The rock cost the dealer $100, but he showed it to a cutter who had a hunch,” Quintero continues. “[The cutter] told the dealer he should check to see what was inside the rock by cutting into the stone and tearing down the piece, destroying the ganga. Though not really convinced, he decided to go for it. Very carefully, the cutter began taking the rock apart, checking where, exactly, and how to cut it. After a few hours, an intense green colour appeared from the rock’s heart. It was a high-quality 15-carat emerald, which was cut into a stunning seven-carat oval shape and then sold for $28,000.”

Which direction?

20.20-carat lab-grown pink sapphire by Robin Callahan.
Photo courtesy Robin Callahan

Gemmologist Boyd Fox (The Gemstone Surgeon), an American Gem Trade Association (AGTA) Spectrum Award winner, specializes in re-cutting and repairing gemstones. He has handled countless stones for his clientele, including some tricky ones.

“I would say, so far, kyanite has been difficult,” Fox says. “Kyanite is a collector’s stone with major cleavage issues, directional hardness, and a few other surprises.”

Like many in this industry, Fox is up for a good challenge.

“I have never said no to a job,” he says. “I like and seek challenges, and my clients know that. I have faceted a lot of weird stuff. Meteorite, human teeth, prosthetic eyes, billiard balls, and a Jolly Rancher.”

The money cut

It may come as a surprise that quartz is not one of Fox’s personal favourites.

“Quartz is one of the worst gems to cut,” he says. “It is somewhat difficult to polish and, since the material is rather cheap, clients do not want to pay much for the labour. Plus, it makes a mess.”

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He has, however, cut some spectacular jewels, including large Burma rubies, Kashmir sapphires, and emeralds.

“The most memorable would be a 30-carat alexandrite. It was a terrible looking stone when I received it,” he says, adding his client originally paid $80,000 for it.

Sunstone from Suncrystal Mining.
Photo courtesy Mike Soebbing/The Gemstone Man LLC

“With proper cutting, it sold two weeks later for over $900,000,” Fox says. “I’ll never forget that one.”

Family affair

Ontario-based cutter, Rudi Wobito (Wobito Gems), and his brother, Ralph, are third-generation master gem cutters with family roots originating in the cutting centre of Idar-Oberstein, Germany. Over the years, Rudi recalls several gemstone species requiring a master’s touch to handle inclusions (like topaz from Ukraine). One of his pieces—an AGTA Award-winning yellow beryl perfume bottle from Volyn, Ukraine—exhibits the stone’s natural etching across much of the bottle’s surface, making it quite striking.

Many claim the brothers are tops at cutting the colour-change diaspore, Csarite (the preferred name), or Zultanite.

“We’ve been cutting this stone since 2005, and, at first, it was quite challenging,” Rudi says.

“The crystals have perfect and distinct cleavage in one direction, much like mica,” he continues. “This presents a problem from a cutting standpoint. You are very limited as to which directions you can actually grind.”

Grinding or cutting in the wrong direction results in the stone simply falling apart in shards, but, Rudi says, there is another consideration to keep in mind with Csarite.

“We need to be aware of the correct orientation for best colour-change, and, of course, best yield,” he explains.

Rudi says the average yield seems to be about 2.5 per cent of the rough, according to his observations from 17 years of working with the material.

“Through the use of some specialized cutting techniques and polishing laps,” he continues, “we have been able take most of the risk out of cutting these stones.”

The first cut’s the hardest

Sunstone from Suncrystal Mining.
Photo courtesy Mike Soebbing/The Gemstone Man LLC

Meanwhile, over in Bainbridge Island, Wash., jewellery artist Robin Callahan of Robin Callahan Designs shares insight into her encounters.

“The most difficult gem I’ve cut was my first lab-grown sapphire for Somewhere in the Rainbow’s annual lapidary event,” she says. “I had only been cutting for a year.”

Callahan agonized, making sure she had the right laps for all phases and issues she might confront. While sapphire is nice to cut in general, the lab-grown element added an extra challenge. Ultimately, when it was finished, the cut pink stone weighed 20.20 carats.

“I learned a ton by being brave,” Callahan says. “I couldn’t pass up that honour.”

Adventuresome as she is, though, the artist says she will not cut opal.

“It’s just too soft,” she explains. “There are cutters who do an incredible job.”

Stories come to life

Callahan has fond memories of working with a “gorgeous piece of green Oregon sunstone rough” while attending master lapidary artist Dalan Hargrave’s Texas ranch for a week of intense learning. This was her first trillion and, late into the night while trying to finish the piece, her dop moved. Ready to throw in the towel, she told herself she would finish it back home. Knowing this would never happen, Hargrave helped her adjust the pattern, and, by 2 a.m., the piece was finished—and Callahan was, too. She took such pride in completing it well that she made it into a pendant, which she still wears.

Every gemstone has a history. Indeed, before these glorious, coloured stones ever found their way into a glamorous piece of jewellery and before a jeweller carefully displayed them in a well-lit showcase, they had a life. Somewhere, a cutter studied each rough and determined to tell its most outstanding story by applying an unremarkable pebble to the cutter’s wheel.

Diana Jarrett is an award-winning trade journalist and graduate gemmologist (GG). A registered master valuer, Jarrett is a popular conference and trade show lecturer. She is also the co-author of Cameos Old & New (4th Edition) and the co-creator of Jarrett can be reached at or via

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