NEW CANAAN — Unimin and its 100 employees will be leaving its Elm Street office building, according to a representative of the nonmetallic mineral producers.

A small for sale sign was recently hung on the exterior of the building at 258 Elm St. Mariane Ceballo, Unimin North American Communications manager, said via email on Tuesday that Unimin informed First Selectman Rob Mallozzi in August of their plans to move.

“We are starting to outgrow our current office space and are exploring opportunities including the possibility of a new open floor plan. The new campus we select will reflect our organizational ambitions in growth, promote an open company culture — as well as collaboration — and drive greater efficiencies in how we serve our customers,” Ceballo said.

She added that, because no building space in New Canaan can meet their standards, Unimin will look to relocate.

Unimin employs between 100 and 110 people in New Canaan and has offices across the U.S., and in Canada and Mexico. According to its site, they are the largest producers of low-iron nepheline syenite used in glass, ceramic, paint and plastics and of quartz proppants for oil and natural gas stimulation and recovery.

Ceballo said they will be selling the building, which they’ve inhabited for 33 years and owned for 23.

“We anticipate selling the building to provide flexibility for our growing business,” Ceballo said.

justin.papp@scni.com; @justinjpapp1