The piece features two separate parts – a rectangular supporting base functioning as a mortar, and a round-bottomed marble stone in place of a pestle on top.
The marble section is rocked back and forth to crush pepper, salt or herbs, and is helped along by hand-carved grooves in its base.
The designers wanted to create a product that would focus on shape and movement rather than just function, allowing users to enjoy a "playful and relaxing" balancing motion. They looked to the shape of spa stones for inspiration.
"We wanted to create something new and different," Fogale told Dezeen, "something that wouldn't look like a grinder but more of a sculptural piece, something to proudly display in the centre of the table with a strong character that would generate curiosity."
The pair previously created a collection of tableware and furniture that looked like stone but was actually made from recycled denim, cotton and paper.
In the creation of the grinder's base, De Allegri and Fogale used recycled stone sourced from StoneCycling, a Dutch company that creates building materials from waste. They chose marble in contrasting colours for the pestle.
"We needed a heavy stone – for us the sound it would make when in contact with the recycled stone part was important, and the smoothness when held in a hand," said Fogale.
"We also needed something we could manipulate on the grinding surface to add extra grip, so marble corresponded very well to all this."
The piece was designed for Airbnb's Makers & Bakers installation, which was curated by Ambra Medda during Milan design week and brought together the work of up-and-coming designers from around the world.
Each of the products on display was designed to be used at a table, as part of a shared meal. De Allegri and Fogale are now working to produce a series of the stone grinders.