Business Owner Name: Jay Address: 104 Davidsons Mill Road. North Brunswick, NJ, 08902 Phone: 732.828.0500 Email: jay@portoslateimporters.com Porto Slate Importers (PSI) has exclusive import rights to the highest quality black slate available in the world from Valongo, Portugal. For 50 years, black slate from the Valongo region, in the district of Porto has best been known for its durability, dramatic appearance, and is the premier choice among architects, builders, contractors, and homeowners.