“IGI is an internationally renowned organization which required [a] larger space to accommodate its growth while retaining a prestigious Fifth Avenue address,” Ted Koltis, Moinian Group’s head of commercial leasing, said in a statement. “We are providing a high-end custom build-out for their new space to match the quality of their tenancy.”

The Moinian Group will build out the tenant’s new offices in space that was previously occupied by the flexible office space provider Knotel, which gave it up after filing for bankruptcy last year. The deal, which closed in March, puts the institute in the 13-story tower between East 45th and East 44th streets, also home to the National Basketball Association store.

IGI, which grades and certifies diamonds, colored stones and other jewelry, will relocate from a smaller space nearby at the Fred F. French Building at 551 Fifth Avenue where it has been in a 20,400-square-foot office since 2012, as Commercial Observer previously reported. IGI plans to move into its new digs by the end of this year, according to the landlord. 

The institute also has space at The Moinian Group’s International Jewelry Center building in downtown Los Angeles at 550 South Hill Street. 

Savills’ Jarod Stern, Brad Wolk and Meghan Marchini represented IGI in the deal. Cushman & Wakefield’s Mitchell Arkin, Omar Sozkesen, Peter Kerans and Joseph Simon and DHC Real Estate Services’ James Cassidy handled it for the landlord. 

Brokers from both sides did not immediately respond to a request for comment.

Celia Young can be reached at [email protected].