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The Batu Hitam (meaning 'Black Rock' in Bahasa Indonesia) prospect was first drilled by Billiton Indonesia in the late 1990?s after being identified as a target through soil geochemistry and mapping exercise over the Lakuwahi Caldera.
Significant gold results were obtained in Billiton?s LWD002 drill hole, see results below, but was not followed up on by the time Billiton made the decision to withdraw from gold exploration in Indonesia. Robust has continued to expand the prospect size at Batu Hitam through detailed geologic mapping and continuing diamond drilling programmes.
Geologic logging of drillholes and mapping shows a stockwork of silica-barite veins controlling the majority of gold-silver mineralisation at Batu Hitam. This stockwork overlies older altered andesitic rocks where Robust has identified significant base metal potential as seen in holes such as hole LWD 030 which intersected the first significant copper mineralisation (4 metres @ 1.1% Copper) at Batu Hitam.
Whilst too early to determine the full significance of the copper intersection in LWD 030, the directors believe that potential exists for substantial copper-gold mineralisation within the Lakuwahi Caldera due to similarities to the high-grade volcanogenic massive sulphide copper deposits currently being developed by Finders Resources (ASX:FND) on nearby Wetar Island.
These results extend the precious and base metal mineralisation seen in holes drilled both by Robust and previously by Billiton Indonesia.
Highlights of the assay results from previous holes are as follows:
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LWD 002 |
44m @ 1.53g/t Au and 27g/t Ag from surface |
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LWD 026 |
51m @ 1.35g/t Au and 25g/t Ag |
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LWD 027 |
50.3m @ 1.08g/t Au and 66g/t Ag |
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LWD 028 |
44.2m @ 1.14g/t Au and 3g/t Ag from 3m |
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LWD 029 |
8.2m @ 0.66g/t Au and 39 g/t Ag from near surface
(Hole abandoned due to ground conditions, to be redrilled). |
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LWD 030 |
23m @ 0.85g/t Au and 25g/t Ag from surface
4m @ 1.1% Cu from 27.2m |
The location of diamond drill holes at the Batu Hitam prospect can be seen in the location plan in below.
Detailed location plan of Robust Resources? Batu Hitam Prospect Drilling to date (09/06/2009)
Click to view enlarged image
Drill Section 318975E showing Gold equivalent values (yellow) and combined Lead + Zinc assays as a percentage (blue)
Click to view enlarged image
The current drilling by Robust has expanded the geological knowledge of the Batu Hitam prospect and demonstrates that mineralisation remains open in all directions.
The exploration programme has also progressed to a new phase with the completion of a pilot hole at Batu Hitam to guide excavation of a bulk-sampling shaft. The bulk sample from this shaft will be used for grade confirmation, metallurgical testwork and density measurements. Collaring of the shaft and excavation has already commenced.
Notes on Batu Hitam Prospect:
Au equivalent = Gold Equivalent Grade = Au grade + Ag grade x (Ag Price / Au Price).
Gold and silver prices as at 22nd June 2009 London market (Au = $924US/oz and Ag = $13.83US/oz)
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