Company chief executive Richard Duffy said the restructuring will leave Petra in a stronger position to focus on optimising the value of its diversified asset base.
The company mines diamonds in South Africa and Namibia.
Petra has partially reinstated notes debt with holders of existing notes, contributing $30 million in new money, each taking the form of a new senior second lien note.
The new notes amount to about $337 million, and the remainder of the notes debt will be converted into equity.
This will result in the noteholder group holding 91% of the enlarged share capital of Petra.
Petra was in a financial rut, which forced the company to put itself up for sale in June.
However, this decision was reversed in October, opting instead for the just-completed debt-for-equity restructuring.
Mathew Nyaungwa, Editor in Chief of the African Bureau, Rough&Polished