The two ships were purchased from compatriot owner Franco Compania Naviera as CN Big Red and CN Jumbos, respectively, in mid-2007 but no price was revealed on the deal.
Online platform VesselsValue.com now values the Red Mistral at $1.64m and the New Mistral at $1.81m.
Primebulk has already started to take delivery of four ultramax bulkers it inked at New Times Shipbuilding in China in 2013.
