As you'd imagine, since the black pearls are not only very small - around 1cm in diameter - but also rather valuable, carving them is exacting work.
But to Jim, who comes originally from the black pearl island of Manihiki, slicing through the precious layers of carbonate holds no fears. Working with incredible precision, he starts cutting a second line either side of the central band to complete his design.
"I don't carve to any set design," he says. "I just study the pearl and think about what will make the best use of its shape, colour and texture. I work completely freehand depending upon what the pearl looks like and how I feel on the day."
Jim's involvement with black pearls goes back to when he was a small boy on Manihiki, in whose lagoon most of the Cook Islands black pearl farms are found, but his carving is rather more recent.
"It started about 13 years ago when I had some rellies coming from New Zealand and I wanted to give them presents. I didn't have much cash so I got some pearl shell and used woodworking tools to cut it into necklaces and pendants and things," he says.
"People seemed to like them so I made a few more and started taking them to hotel giftshops to sell and it grew from there."
Jim says that when he first started carving black pearls, as opposed to pearl shell, "I only used flawed pearls and the carvings were mainly to cover up the flaws. Now the carved pearls are so popular we use good pearls."
But if Tokerau Jim's pearl carving business is going well the same can't be said for the Cook Islands' black pearl industry as a whole.
Back in 2000, black pearls were one of the country's major earners, bringing in $18 million a year, but since then a combination of a disease outbreak in the pearl oysters, the global economic downturn and over-production in Tahiti - the other major player in the black pearl industry - has seen sales slump to as low as $6 million a year.
That's a particular concern to Cook Islands Prime Minister Henry Puna, not only because of the effect on the economy, but also because, as I discovered during a chat at his office, before going into politics he ran a pearl farm in Manihiki for 15 years.
The pearl industry is having a tough time, he agrees, but there are hopes that a recent agreement with New Zealand to spend $3 million over the next three years to boost the industry will put it on a sustainable footing.
That will involve a major effort to "monitor and manage the fragile ecosystem that produces the Cook Islands black pearl" and "an improve marketing performance to sell our black pearls to the world".
If all goes to plan, then, there should be beautiful black pearls for Jim to carve as long as his eyes stay sharp enough.
"When I was young," he says wistfully, "I could carve a pearl in an hour. Now I'm 40-plus my eyes are not so good and it takes three or four hours. But if my eyes get worse I guess I could always get glasses."
CHECKLIST
RAROTONGA
GETTING THERE
Air New Zealand flies from Auckland to the Cook Islands six times a week, with airfares starting from $265 each, one way. For airfares and holiday options visit airnewzealand.co.nz.
FURTHER INFORMATION
www.tokeraujim.co.nz
* Jim Eagles visited Rarotonga with help from Cook Islands Tourism, Air Rarotonga and Air New Zealand.
