Grolleg, also known as English china clay, is a kaolin that is mined in Cornwall. Kaolins are also called china clays because the word kaolin stems from the name of a Chinese mountain where the high-quality clay was first mined. The word grolleg, however, is of uncertain etymology.

Situated in the southwest peninsula of the United Kingdom, Cornwall is geologically quite complex and thus has a rich and extensive human history of mineral extraction. The Cornovii were a Celtic tribe whose name translates to “people of the horn,” referring to the peninsula that they inhabited. Known since antiquity for its deposits of tin and copper, Cornwall saw its first large-scale kaolin industry develop in the late 18th century. The region has been a major producer of kaolin clays for well over 200 years, and the UK currently stands as the third largest producer and exporter of kaolin in the world.

In studio ceramics, grolleg is mainly used in porcelain bodies, its key useful component being its low titania content. Grolleg can be found in formulations of tableware and electrical porcelain, but the kaolin produced in Cornwall ends up in a variety of other fields, such as cosmetics, plastics, rubbers, and even paper.

The multinational conglomerate Imerys mines grolleg kaolin in Cornwall at the extensive Saint Austell mining complex, home to many other extractive and industrial companies. The Cornwall Mining Alliance, which includes Imerys, is a coalition of these companies, covering many extractive materials from granite to aggregates to sea salt.

Kaolin in Cornwall has traditionally been mined using wet mining processes, where high-pressure water strips the mine walls of clay, allowing the slurry to pond at the bottom of the mine before it is pumped out for further processing, similar to EPK. Recently, however, Imerys has switched to the less energy-intensive and more precise method of dry mining, which consists of breaking chunks of material off the mine walls with machinery before moving them to a processing facility.

Imerys mines and processes grolleg at its Saint Austell facilities before shipping the material from an unknown UK port across the Atlantic Ocean to a port in New York City. From here, the grolleg travels to Hammill and Gillespie’s warehouse in New Jersey where it sits until it is purchased by Rocky Mountain Clay in Denver. Once the grolleg reaches Denver, it goes on to Colorado State University. An estimate of its total travel mileage is about 5,500 miles.