It was a nominal purchase on confidential terms, with both parties signing a deed of indemnity and release which divests the five subsidiaries - Australian Solomons Gold, Solomon Islands International, JV Mine, ASG Solomon Islands and Gold Ridge Mining - associated with the Gold Ridge project.
As a result, St Barbara will reverse some balance sheet reserves and provisions, which will be finalised in its year-end reporting.
The company has no residual provisions for environmental or rehabilitation liabilities in relation to the project.
Managing director and CEO Bob Vassie said: "The sale of the Gold Ridge mine to a locally owned company with strong landowner representation provides a fresh and realistic opportunity to successfully manage the critical security, local resourcing and environmental issues that Gold Ridge must resolve in the near term."
"Representatives of GCIL first approached us about buying Gold Ridge in February 2015, when the Solomon Islands government advised it was no longer interested in buying the mine.
"Many of the shareholders and directors of GCIL have had personal associations with, and concerns for the success of, the Gold Ridge mine since it was first established in the mid-1990s, with the GCIL chairman being a former Minister of Mines and Energy."
St Barbara has agreed to fund, manufacture, deliver and install a replacement water treatment plant as part of the agreement with GCIL. Construction is expected to take about four months at a cost of $A1million.
The company has also agreed to provide technical advice and assistance for six months following the sale.