A German-based company that for years has quietly transported clay slurry to Maine for use in the paper mill industry put the spotlight Sunday on one of its newest cargo vessels, providing the public a rare look into the global maritime industry that makes Portland Harbor one of the state’s busiest ports.

The company, MST Mineralien Schiffahrt, based in Schnaittenbach, Germany, held an unusual naming ceremony late Sunday afternoon at Portland’s Ocean Gateway Terminal for the MV Marguerita. The ship is named after a New York City woman, Marguerita DeLuca, whose husband, Matthew, a shipping broker, has known MST’s founder for 45 years.

Clay slurry has been shipped by MST to the ports of Searsport and Portland for about 20 years, officials familiar with the company said. Clay slurry from Brazil supplied by Imerys, a company based in Savannah, Georgia, is used for specialized paper coatings in Maine’s paper mills. The slurry solution provides a glossy, smooth surface to the paper product.

Aside from the people who work in the port of Portland, cargo ships the size of the MV Marguerita – which is 185 meters long, or about the size of two football fields – largely go unnoticed. And if they are noticed, not too many people can guess what the ships are carrying.

“People notice all the cruise ships and tankers, but this cargo ship represents the other side of Portland Harbor. They slip in under the cover of darkness, before they ship out again,” said Capt. Shawn Moody, agency operations manager with Chase, Leavitt & Co. of Portland.

Moody’s firm acts as MST’s local shipping representative, making sure that ship arrivals and deliveries are coordinated with port authorities and local vendors.

The MV Marguerita was built in China and set sail on its maiden voyage in February. The ship made its first visit to Portland on March 9 and returns every 25 days, offloading its cargo at the Sprague Terminal in South Portland.

Moody said the fact that MST chose Portland as the place to christen its new ship is an honor.

“The owners could have done this in China, but instead they chose Portland. It’s something Portland should be proud of,” Moody said.

Markus Hiltl, MST’s chartering manager, introduced the ship’s captain, Paul Lukac, and his crew to a crowd of about 50 people who attended the ceremony at the Ocean Gateway Terminal. Hiltl said that on the guest list were people from all over the world, including China, Canada, Italy, the United Kingdom, Germany and the Netherlands.

Hiltl said the MV Marguerita, in addition to Brazil, has sailed to Vancouver, British Columbia.It also was designed to navigate through the Great Lakes Waterway, a system of channels and canals. It is manned by a crew of 21 sailors.

Matthias M. Ruttmann succeeded his father, Jürgen W. Ruttmann, in 2009 as MST’s owner. Matthias spoke at the ceremony.

Ruttmann said his father, who could not attend the ceremony, believes that naming a ship, an old seafaring tradition, is still important.

“Why should we christen a piece of steel?” Ruttmann asked. He said naming a ship is important to the crew, which can face all sorts of dangers on the open sea.

“In a situation of stress and danger, the crew will be happy to think of someone who will hold their hands, mentally of course,” Ruttmann said.

Marguerita DeLuca wished the crew calm seas and safe passage before cutting the rope that held a bottle of champagne suspended in midair. After cutting the rope, the bottle smashed against the hull. Ship tours and a private reception followed the christening ceremony.