The diamond hit of 5.65m at 80 grams per tonne gold from 160m included 1.1m at 404gpt gold.
The company said the intersection is interpreted to be the main lode extension that historically produced 77,000 ounces of gold at about 22gpt.
"This is a very exciting result and demonstrates the extremely high-grade nature of this deposit; in fact it's the highest-grade intersection recorded in any drill data at Cox's Find to date and it has come from Great Southern's first diamond program," Great Southern chief operating officer Mark Major said.
"This now validates our view that this deposit has an extremely high-grade component to it which requires the application of modern-day exploration techniques to define its extent."
Assays for a further four diamond holes are pending.
"We are getting a good indication that the mineralisation is persistent at depth and along strike," said Major.
"The focus now is to trace the high-grade component down-plunge along strike to expand the deposit. If we are successful in this next phase, then the full extent of this asset will start to become evident."
Yesterday Great Southern applied for four tenements adjacent to Cox's Find, which would increase its tenure 16-fold to 54sq.km.
The company is also drilling its Mon Ami project near Cox's Find, and is conducting field work at Edinburgh Park, near Mt Carlton in Queensland.
Great Southern shares started the year at A7c and rose as high as 19.5c on July 1. The stock was up 3.1% this afternoon to 16.5c, valuing the company at $66.3 million.