Geological Survey of Victoria estimates the state’s goldfield geology is two orders of magnitude (100x) richer in gold than the global average, and that recent successful mines like Fosterville and Costerfield show the state has more than 48 million ounces of gold still to be found and mined.

Modern exploration techniques including magnetics, conductivity and other geophysics give an added impetus to exploration and mineralisation research.

Science combined with conviction, persistence and patience are the keys to unlocking Victoria’s golden opportunities – Fosterville has shown the prize is worth the risk. One deposit has increased Victoria’s share of Australian gold production from 1.5% to 5.6%.

Grade estimation

Victoria’s often nuggety, coarse gold makes new exploration technologies like those being employed by WGL especally important.

For example, during 1989, Western Mining Corporation carried out an evaluation of the Poverty Reef at Tarnagulla. A 970-tonne bulk sample yielded a head grade of 7 g/t. Diamond drill core assays from both surface (NQ) and underground (BQ) drilling indicated a low grade in the 1 g/t to 3 g/t range. As a result, Western Mining chose to downgrade its exploration at Tarnagulla, put its operations in care and maintenance and release its subcontractors.

In 1994 Reef Mining discovered the Nick O’Time structure by surface diamond drilling on a 50-metre grid pattern along an interpreted south plunging zone south of the Poverty Reef workings. Grade estimates during exploration ranged from an original estimate of up to 10 g/t to between 5 g/t and >20 g/t.

The figure at right shows the difficulty of estimating grade in this setting with face-sample assays wildly fluctuating from an extraordinary 759 g/t to 0.05 g/t.

Reef Mining NL mined the Nick O’ Time Shoot for a yield of 57,000 tonnes and 53,000 ounces of gold at a grade of 29.1 g/t.

Figure: Reef Mining NL The Nick O’ Time Shoot produced very high-grade ore despite the low grade indicated by Western Mining’s initial drilling.

Figure: Reef Mining NL mining stope, Poverty Reef.