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Jul 19, 2005
Positive Metallurgical Test Results from Archangel Gold-Silver Prospect
Mindoro Resources Ltd. (TSXV: MIO; Frankfurt: OLM) reports that high gold recoveries were obtained in column leach tests of coarse-crush mineralized material, over a short leach period, for a small bulk sample from the Archangel gold-silver prospect, Philippines. Mindoro is carrying out more detailed evaluations aimed at establishing the open-pit, heap-leach potential of the prospect.
Epithermal gold-silver mineralization at Archangel in quartz stock-works of varying intensity, hydrothermal quartz breccias and massive replacement quartz, is associated with gold-in-soil anomalies that extend semi-continuously over at least four kilometers by one kilometer. Geological mapping and reconnaissance rock sampling has traced the mineralization a distance of at least two kilometers.
Previous drilling in the 1990s, carried out in a small part of the prospect, intersected low-grade gold mineralization averaging about 0.7 grams per tonne (g/t) in an area of approximately 600 meters by 400 meters. Mineralization is open in several directions. Since the mineralization is near-surface and within the grade ranges being heap-leached elsewhere in the world, Mindoro is carrying out an evaluation of the open-pit, heap-leach potential of the prospect. Preliminary bottle roll metallurgical test work reported on January 14, 2004, was largely positive.
For this second phase test, a 245 kilogram sample was collected from a trench and submitted to Metcon Laboratories in Australia. Head grade was 3.58 g/t gold and 51 g/t silver. The material was crushed to 12.7 mm (0.5 inch). Approximately 20.61 kilograms of material were leached in a column 1.85 meters tall. The material leached exceptionally well, with 87.1 percent extraction of gold after only seven days. This high gold extraction is exceptional and not much less than the 94.4 percent obtained in a CIL test at a grind of 80 percent passing 75 microns.
Highest gold grade and gold extraction were obtained from the coarsest fraction (-50 + 37.5 mm), indicating a coarser grind could be used. A coarse crush size would reduce costs and improve heap agglomeration and percolation. A new test is under way using a coarser crush size. It appears that cement, instead of lime, can be used as the agglomerating medium. The silver extraction at 6.8 percent was very low, despite the high silver head grade, and more tests are required to reach a conclusion on the amenability of silver to leaching. Silver recoveries are characteristically low in gold-silver heap leach operations.
In conjunction with planned drill-testing of promising porphyry copper-gold targets below the epithermal gold mineralization (see news release dated March 15, 2005), non-oxide samples will be collected for leach testing. The previous bottle roll testing of non-oxide material indicates at least some of the non-oxide material leaches well (see news release dated January 14, 2004). Geological work, to be followed by drilling, is in progress to establish the resource potential of the Archangel gold-silver prospect.
Mindoro management is encouraged by the results from Archangel to date and considers these a strong basis for further evaluation of the project's economic potential. The program is carried out under the supervision of Mr. J. A. Climie, P. Geol., and a "qualified person" as defined by National Policy 43-101.
At the Lobo Project, seven kilometers from Archangel, drilling progress on the Pica porphyry copper-gold prospect has been slowed down by difficult drilling conditions, near a depth of 430 meters, which are related to intense hydrothermal alteration and high clay content in places.
Mindoro is a Tier One Company trading on the TSX Venture Exchange (TSXV: MIO) and the Frankfurt Stock Exchange (OLM). The Company is exploring for gold and gold-copper in the prolifically mineralized magmatic arcs of the Asia-Pacific Region. Mindoro has been active in the Philippines since 1996 and is presently focused on six promising projects in politically stable jurisdictions of the Philippines.
For further information, contact
Penny Gould, Executive Vice President
Marshall Farris, Ascenta Capital Partners Inc.
Toll Free: 1-866-684-4209
The TSX Venture Exchange has not reviewed and does not accept responsibility for the adequacy or accuracy of this release.
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