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Deposit Synonyms
Bendigo; Kia Ora; Kia-Ora
Mineral District
Deposit Summary
large resource of white kaolinitic clay derived from weathering of underlying Bendigo granite. Testwork on 2 samples indicated variable reflectivity. 1 sample from hole KR23 with 50% halloysite in the 2 micron fraction.
Deposit Description
FRANKLYN, widespread thickness of white kaolinitic clay derived from weathering of underlying Ordovician Bendigo granodiorite - adamellite, were identified during several phases of bedrock drilling by the Geological Survey in the 1970s, and in 1992 over an area of >50km2. It was estimated that white kaolinitic clay had been penetrated in 66 of 179 holes drilled. The drilling inferred large resources of white clay were available, with pattern drilling required to further evaluate the resource size.
Two samples from holes BH10A, and KR23 were sent for testwork to determine their suitability for use as paper coating clays. The white clay intervals tested included 13.14 m, from 14.63-27.77 m in hole BH10A, and 9 m from 21-30 m in hole KR23. Reflectivity value was 66%, which is considered too low for use as paper coating clay. Firing tests revealed moderately refractory properties, but firing crack developed at temperatures >900 °C and the fired colour is grey at 1200 °C, which renders it unsuitable for use in fine ceramics.
The sample from KR23 revealed a reflectivity of 85.7%, and poise viscosity of 50.7%. The low viscosity concentration was caused by up to 50% of the kaolinite in the minus 2 micron fraction being in the form of halloysite. Halloysite is detrimental in coating clays due to its tubular habit.
In 2019, Archer Materials Ltd conducted a review of historical drillholes. Thirty-nine composite samples from 12 drill holes were screened at three size fractions of >53µm, 53-45 µm and <45 µm, with assay results indicating majority of the kaolin within the >53 µm and <45 µm fractions. The <45 µm fraction yielded an average grade of 33% Al2O3, 47% SiO2 and 3% Fe with a 53% recovery. Archer Materials established a maiden kaolin exploration target of 45 to 91 Mt at a grade of 30 to 36% Al2O3 (<45 µm size fraction).
Chemical analysis of the halloysite-kaolin at Franklyn shows a 30-50% higher aluminium concentration than typical halloysite-kaolin products, making it a suitable feedstock in high purity alumina production. The halloysites also have large lumens, making them suitable for applications requiring high loading of gas, liquid or nanoparticle, and high value ceramics including additives that improve the mechanical reinforcement of advanced composites.
The area has been of interest for decades for its prospectivity for porphyry-style copper mineralisation. Kia-ora Minerals PL in the late 2000s interpreted aeromagnetics as indicating a complex, multi-phase granite intrusion. They drilled 5 holes on magnetic anomalies to test for skarn-hosted mineralisation for no significant mineralisation penetrated. Of interest is hole 82FN3RM1 that penetrated very weathered andesite/andesitic basalt interlayered with limonite-magnetite clay, with elevated copper (200-910ppm), manganese to 2.5%, and gold (to 0.14ppm).
Discovery Year
? 1973
Commodities
Kaolin
Ore Minerals
Halloysite, Kaolinite
Gangue Minerals
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