Over the past few years an unlikely material has found its way into wetsuits: limestone. One would think that using rock to create rubber might cause a wearer to sink, but the porous yet closely-packed cells found in a limestone-based rubber is said to make the wearer more buoyant.

De Soto Sports, a San Diego-based company that makes clothing and gear for triathlons, developed its own brand of limestone-based rubber, GreenGoma, to use in its wetsuits. Starting with the 2012 line, which first hit stores this past fall, all of the company's T1 wetsuits are made with GreenGoma, which eliminates the use of petroleum products in the line.

While many triathlon competitors will be interested in a petroleum-free wetsuit, GreenGoma reportedly provides a number of other benefits to the wearer - the material is claimed to provide suits with increased stretch, buoyancy, durability and insulation.

Increased buoyancy is due to a closed-cell injected construction, which makes it 98.9 percent water impermeable. De Soto Sports founder Emilio De Soto compares the suit to cork. "If you have a really dry sponge, it almost feels like a crispy piece of bark. If you put that sponge in water it will float until it reaches the saturation point and begins to sink," he tells Gizmag. "The cells in cork are so closed to water it doesn't permeate. Like cork, that baby's still going to float."

T1 Wetsuits are not the first to market with limestone-based rubber. Companies including Matuse and Patagonia use the stone to produce wetsuits, however those are designed for surfing. De Soto's T1 Wetsuits are made specifically for swimming in triathlons. Wetsuits used for triathlons and swimming allow the wearer to stretch and go through the motions of swimming strokes with ease. The suits also tend to offer a certain amount of buoyancy.

The limestone-based rubber has existed for a few years, but in order for De Soto to use the material, it had to adapt the limestone material for its needs, which are stretch, buoyancy, durability and insulation. De Soto worked with suppliers to develop what it's branded as GreenGoma.

Does this mean the use of limestone-based rubber is a green option? De Soto believes it is a better option than petroleum-based materials, yet he realizes there is a finite amount of limestone, and hopes another option will come along.

"We've stepped away from petroleum. We're using limestone," says De Soto. "Years ago it was not possible to make rubber from limestone. Maybe in a few years something else will come out with the same effect."

It's still early for feedback, but some initial results from independent testers indicate that the current T1 Wetsuits are about three seconds per 100 meters faster than suits sold a few years ago. The credit is shared with GreenGoma and other elements of the suit. "Part of it is the material, another part of it is the fact we've extended our research to get the human body to propel itself more efficiently in water," says De Soto.

One-piece and two-piece T1 Wetsuits sell for about US$200 to $320 at De Soto Sport.