Classic chairman John Lester said the ministerial approval was the final remaining hurdle required and the company was poised to begin full scale mining and processing gold ore using its own on-site facilities.
Processing approval covers installation and operation of a gold circuit, gold room, product sampling, dewatering, crushing circuit, Gekko gravity circuit, tailings storage facility, fuel systems, processing control systems and high voltage power.
About 10 construction and 50 ongoing jobs will be available at Kat Gap.
Classic signed a deal with Perth company Goldvalley in September for $10 million in funding, with Goldvalley to receive a 30% share of the net profits from gold production at Kat Gap.
Recent metallurgical and processing test work on Kat Gap ore showed a traditional gravity circuit and cyanide leach plant could achieve recoveries of about 98%.
Kat Gap hosts a shallow unmined gold deposit first discovered in the 1990s by Sons of Gwalia.
Classic plans to mine in three stages targeting mineralisation at just 7m below surface, based on Kat Gap's existing 93,000 ounce resource.
Once the Gekko plant is ready Classic plans to process a 6500 tonne stockpile that grades 6 grams per tonne gold to produce a bar of dore that will be sent for refining at the Perth Mint to generate early cash flow within 12 weeks.
Lester said when the plant opened it would be the only other gold processing plant in the region, apart from the Marvel Loch gold mine.
"The company would like to thank its approvals team for the efforts working through this complex approval process which is consistent with our environmental, social and governance approach, also our commitment to operating in a way that is safe for our people, our communities and the environment with an objective to contribute positively to the communities in which we operate," he said.
"Mining and processing [at Kat Gap] provides a low capex pathway forward while retaining a solid proportion of the profits and avoiding dilution."