The pink argyle and white diamond ring, valued at 577,000 Australian dollars, was taken from a display counter at Theodore Bruce Auctions in New South Wales.
It is estimated that around 100 people walked through the auction centre during that time.
An attendant discovered the ring was missing and immediately contacted police. The investigations in the case are going on.
The police had not been able to acquire CCTV footage of the theft, however, the diamonds on the ring have been laser-inscribed with a serial number, Sydney Morning Herald reported.