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Underneath the vast sky and sparkling waters of the Sea of Japan lie rich deposits of diatomite, accumulated from long ages past when this was an inland sea. Suzu, the city at the tip of Noto peninsula in Ishikawa prefecture, draws on these siliceous fossil remains to produce lightweight, all-natural charcoal burners.

It’s a story that goes back some 20 million years or more, to the Miocene Epoch. Back then, the Sea of Japan was a landlocked body of water. Fed by thermal springs created by volcanic activity, it was an environment ripe for the growth of diatoms, a major group of single-celled planktonic algae. When an explosive bloom of them depleted nutrients in the water and blocked out the sunlight needed for photosynthesis, diatoms started to die off, their remains sinking to the seabed. Those deposits then fed a new generation, which led to another bloom, and so on. As theory has it, this oft-repeated cycle of planktonic boom and bust is what formed the massive strata of diatomaceous earth—also known as diatomite—now found in the area.

Consisting almost entirely of silica, these sedimentary deposits are characterized by their low density and high porosity. Diatomite’s excellent absorbency and insulating properties make it an ideal material for filters, heat-resistant bricks, and grills—and Suzu is a major production center for them all.

Situated at the northeastern tip of Noto peninsula, Suzu is in fact Japan’s largest producer of diatomite. The sedimentary deposit in the area is estimated to reach 5.1 billion cubic meters in volume; at its deepest point it extends as far as 400 meters below the ground. At one of the excavation sites overseen by the mining firm Noto Daiya Kogyo, we photographed a veteran quarrier as he progressed steadfastly through a dimly lit shaft.

Diatomite strata are not found by scientific measuring, but by information passed along by local elders who have long been in the business. Until the 1960s, hundreds of people were involved in diatomite mining in Suzu, but today only a few remain. Following the leads of veteran quarrymen, the mining company decides where to focus its operations. The site we visited was relatively new, extending only 20 to 30 meters, but others are labyrinthine. Because the quarries are so narrow, workers dig alone, carving their way through tunnels that can eventually stretch to as long as 500 meters.

Alone at his task, a quarrier etches a precise grid on the wall where diatomite is exposed. In short time the outlines of future bricks appear beneath his chisel. Driving a wedge into the grooves, he extracts one freshly cut block after another. A notable feature of diatomite bricks produced in Suzu is that they are baked without undergoing pressing. Each day’s take goes straight into a kiln and emerges ready for market or further processing.

Kaginushi Kogyo K. K. produces diatomite charcoal burners in a building formerly used for silkworm cultivation. While diatomite bricks account for most of the firm’s sales, a corner of the factory is given over to the manufacture of its Charcoal Konro Grills—accomplished wholly by hand, piece by piece. President Tetsu Kaginushi comments, “The hot grease and juices that drip during grilling cause regular burners to give out fairly quickly. But these grills are made of diatomite bricks that have baked at 1,000°C for six hours. Having endured those temperatures, they are ready for anything—they’re very durable.”

Stacked piles of diatomite bricks move along a conveyor belt on their slow journey through the factory’s long kiln. Afterwards, a workman hits each fired piece with a hammer to judge by its sound whether there are any cracks within. Whereas some makers join bricks with mortar to form their cooking grills, at Kaginushi the workmen use carpentry skills to fit each unit together meticulously by hand, for a stronger, tighter, more fire- resistant product. Because diatomite grills have superior heat-insulation properties, charcoal used in them starts easily and burns longer than in conventional cookers.

Cookware crafted from diatoms. It gives us pause to think of the vast sea and the countless unicellular organisms that have metamorphosed over and through the ages to appear in this new form for our use today: a tool that’s strong enough to withstand the burning of charcoal, itself the product of wood transformed by fire.

Quarried diatomite bricks move along a conveyor belt to bake slowly in the kiln. Tetsu Kaginushi, the president of Kaginushi Kogyo, is shown on the top right.