There is no doubt that water ingress, harder rock and shonky deals all contributed to loss of confidence in the field. However these reasons of themselves do not distinguish the Castlemaine field.

We consider that the three major reasons why the Castlemaine field was not developed at depth were:

• The wealth of the alluvials - some 3 million ounces were won in the first 10 years of the first mining boom.
• Over-use of the Bendigo model - our research has shown an inadequate geological understanding of the major structural controls on gold mineralization. When deeper mining was attempted, in most instances the target was repetitive vertical saddle reefs but saddle reefs formed only a small proportion of the goldfield's past production compared to near surface spur and laminated quartz veins.
• Beaten by time - by the time the alluvial fields and shallow workings were worked out, changing economic circumstances and the outbreak of war closed down the remaining mining operations.

Two examples to support our contention that the old miners did not have sufficient understanding of the major structural controls can be seen in the old Ajax and Quartz Hill mines.

Ajax Mine Example;

The Bolivia shaft had early success at shallow depth on a west dipping fault. Using the Bendigo model, capital was raised to sink deeper looking for the next repeat. A number of levels were developed from the Ajax shaft with cross-cuts into "centre country". The poor returns from deeper prospecting resulted in the perception that grades reduce at depth. This reef would have become bedded in the western limb of the anticline.

Quartz Hill Mine Example;

At Quartz Hill a massive quartz structure was accessed through an adit. An 1885 report by the District Mines Surveyor proclaimed Quartz Hill to be a "great saddle reef in every respect". Grades of 2-30 ounces were won from the first 50 feet. The shaft was sunk to 119m in 1859 but the mine closed after flooding. Dewatering of the mine occurred again from 1893 to 1904. The shaft was sunk to 159m with long drives extended along the eastern, west dipping fault.

The large mass of spurry quartz formed between the Quartz Hill Fault and Thompsons Fault. These structures have locally displaced the anticlinal and synclinal axes. The company lost heart when faced with the amount of dead work to sink deeper onto the next saddle reef. There was a misinterpretation of the west dipping faults as anticline legs and the large quartz blow-out as a saddle reef.

Wattle Gully Evidences this Inadequate Understanding

We submit that the very fact that the Wattle Gully mine was not found by the early prospectors evidences the potential of the Castlemaine field at depth.

In 1853, quartz mining commenced on a reef located on the west bank of Wattle Gully. During the late 1850s and 1860s, various companies were formed to explore and exploit the reef (Phillip's Reef) along Wattle Gully and during the next twenty years, numerous shafts were sunk, generally to a depth of less than 350 feet.

Leases were small and the field was fragmented between many different groups so that as the shafts became deeper, larger sums of capital were required and mining proceeded in a most inefficient manner whilst exploration languished badly due to lack of funds.

The depression of the late 1880s saw capital dry up completely and mining began to decline. Manpower became scarce after a Royal Commission into miner's health in the early 1900s and the Great War in 1914 finally finished the industry off. During this first 30 - 40 years of sporadic mining only 25,620 ounces of gold were produced from the reef.

The Wattle Gully shaft was reopened in 1933 by Wattle Gully Gold Mining Company N.L. to prospect the old diggings. In 1934, a Government assisted diamond drilling program intersected 3.96m of quartz assaying 154.5g/t of gold in what they thought was the down dip extent of Phillips Reef.

The sinking of the shaft to 180m depth and lateral development revealed this interpretation to be incorrect, and that the drill hole had severely deflected off course to intersect an unknown quartz reef formation of major proportions.

This intersection now known as the Wattle Gully Fault Reef, one of the most successful in Victoria, may never have been discovered had the drill hole not deflected so far off course.

So it was, after 30 years of sporadic mining with gold production of only 25,600 ounces and 40 years of relative inactivity that a quirk of fate lead to the discovery of one of Victoria's largest single gold mines.

 
Wattle Gully mine cross section looking north as it would have been seen in the 1930's