Subscribe for Updates:

Enter your email below to receive email updates

RSS Feed:

Press Releases

Jul 17, 2007
Excellent Final Metallurgical Results from Kay Tanda
EDMONTON, Alberta; July 17, 2007 - Mindoro Resources Ltd. (TSXV: MIO; Frankfurt: WKN 906167) today reported it has received excellent final results from extensive metallurgical testwork of drill core composites for two different crush sizes from both oxide and mixed (transitional) oxide and sulphide mineralized material from the Kay Tanda gold-silver prospect, Philippines. The independent metallurgical consultant noted that "the heap leach results are remarkably good in all cases, with recoveries (of the coarse crush) only approximately 10% below the maximum gold recovery achievable by grinding to a fine size."

Results to date indicate that both composites are highly amenable to heap leaching. It appears that most of the gold occurs in the cracks and fissures in the rocks and is readily accessible to the cyanide solution. Gold dissolution is rapid and high gold recoveries have been obtained from both composites, and with low cyanide consumption.

Kay Tanda is being evaluated for its open-pit, heap-leach potential. Preliminary bottle roll metallurgical test work on reverse circulation cuttings was largely positive (reported on January 14, 2004). A second round of testing was carried out on a small bulk sample of oxidized mineralized material from a pit and gave excellent results (reported on December 2, 2005). The current test had the objective of evaluating heap leach characteristics of near-surface oxide mineralization, as well as deeper mixed oxide/sulphide (transition) mineralization. Samples were collected by large diameter (PQ) core drilling and submitted to Metcon Laboratories, in Australia. The program was designed and supervised by an independent consultant, Peter J. Lewis and Associates of Australia. A summary table of results appears below. The full report will be posted on the Mindoro website in the near future.

Column tests (heap leach tests) were performed on a crush size of minus 12.7mm, i.e. 1/2 inch, which is close to the lower size limit normally used for heap leaching. Gold recovery from the oxide material after 29 days of leaching was 82.4% and for silver 32%. Silver recoveries are normally low and in this range for heap leach operations. Gold recovery from the transition material after 23 days was 78.3%, and silver 42%. Both composites are highly amenable to heap leaching.

Because of the encouraging results a further test was commenced at a very coarse crush size of 50mm (2 inches), since the coarser the crush, the lower the processing costs. Gold recovery from the coarse oxide material after 70 days was still a very high 80.7% and 29% silver. Gold recovery from the transition material after 70 days was 80.1% and for silver 56%. Since the transition sample contained a high proportion of sulphide-related mineralization, and leached very well, a test is also being carried out on deeper, entirely sulphide-related gold and silver mineralization as well.

Mindoro management is most encouraged by the results from Kay Tanda to date and considers them a strong basis for further evaluation of the project's economic potential. Preliminary work on a National Instrument 43-101 resource estimate has commenced, to be followed by a scoping study.

The program is carried out under the supervision of J. A. Climie, P. Geol., President of Mindoro and a "qualified person" as defined by National Instrument 43-101. Metallurgical reports will be posted on Mindoro's website on completion of all testwork.

Ore Type Crush size (mm) Leach time (days) Calculated Head g/t Au Residue grade g/t Ag % Recovery g/t Au Reagent consumptions (kg/t)
g/t Au g/t Ag g/t Au g/t Ag Au Ag Cement Cyanide NaOH
Oxide minus 12.7 29 1.14 3 0.2 2 82.4 32 2 1.43 0.46
minus 50 70 1.09 3 0.21 2 80.7 29 2 1.42 0.35
Transition minus 12.7 23 1.06 2 0.23 1 78.3 42 3 1.47 2.69
minus 50 70 0.95 1 0.19 0.5 80.1 56 6 1.57 0.62


Ore Type

Calculated Head

Residue grade

% Recovery

Reagent consumptions (kg/t)


g/t Au

g/t Ag

g/t Au

g/t Ag























Epithermal gold-silver mineralization at Kay Tanda is associated with extensive and intense quartz stockworks, veins and hydrothermal breccias, with accompanying base metal sulphides. Kay Tanda is reflected by an induced polarization chargeability anomaly that is about 1.5 kilometers by 1.4 kilometers in extent, which is part of a much larger chargeability anomaly which extends over six kilometers along strike to the northeast. To date, drilling has been conducted only on the Kay Tanda part of the trend.

Mindoro has completed over 150 reverse circulation (RC) and twenty core drill holes at Kay Tanda. Almost all holes have encountered near-surface, generally flat-lying to gently-dipping blanket-like low-grade stockwork mineralization. This is strongly to partially oxidized to depths of 40 to 160 meters and non-oxide below this. Drilling, especially at deeper levels, has encountered at least five steeply-dipping, much higher-grade zones with bonanza grades to 246 g/t gold and over 1,000 g/t silver, which are interpreted as structurally controlled upflow, or "feeder" zones. Further drilling and structural studies are in progress to determine the nature and controls of the high-grade zones. The high-grade mineralization appears to occur preferentially at elevations below 150 meters (ASL) within a boiling zone. Few holes have penetrated to this depth to date. Such upflow zones can be associated with bonanza mineralization and constitute some of the world's best epithermal gold-silver deposits.

At a cut-off at 0.3 grams per tonne (g/t) gold, the immediate Exploration Target is from 35 to 40 million tonnes of open-pitable material at a grade of 0.76 to 0.80 g/t gold and 2.4 to 2.8 g/t silver, containing between 860,000 and 1,000,000 ounces of gold and 2.7 million to 3.6 million ounces of silver. This Exploration Target may be revised upwards at a later date as extension drilling continues with two diamond drill rigs at Kay Tanda. At a cut-off at 0.5 g/t gold, the immediate Exploration Target is from 15 to 20 million tonnes of open-pitable material at a grade of 1.1 to 1.4 g/t gold and 3.0 to 3.4 g/t silver, containing from 530,000 to 900,000 ounces of gold and from 1.45 to 2.2 million ounces of silver.

Kay Tanda is being evaluated for its open-pit, heap leach potential. Initial metallurgical test work has produced excellent results. Kay Tanda is interpreted as intermediate to low sulphidation epithermal quartz-carbonate-gold-silver-base-metal mineralization telescoped into the top of an underlying porphyry copper-gold system.

Programs are carried out under the supervision of Tony Climie, P.Geol., who is a qualified person as defined by National Instrument 43-101. Sample preparation and assaying is performed by McPhar Laboratory of Manila, an ISO 9001/2000 accredited laboratory. Gold assays were by 50 gm fire assay fusion; where gold assays greater than 3 ppm were by gravimetric finish, and by AAS where the gold values were less than that threshold. Silver was determined by AAS after an HCl-HNO3-HClO4 digest. Normal Quality Control and Quality Assurance procedures are being carried out, using a system of duplicate, standard and blank samples.

The reader is cautioned that the potential quantity and grade of the Exploration Target described is conceptual in nature, that there has been insufficient exploration to define a mineral resource and that it is uncertain if further exploration will result in the target being delineated as a mineral resource. Until a feasibility study has been completed there is no certainty that the Company's projections will be economically viable.

Mindoro is a Tier 1 Issuer trading on the TSX Venture Exchange (MIO) and the Frankfurt Stock Exchange (WKN 906167). The Company is carrying out three major drill programs: resource delineation and expansion drilling on the Kay Tanda epithermal gold-silver prospect where a NI 43-101 compliant resource estimate is in progress; reconnaissance drilling on the Calo porphyry copper-gold prospect; and advancing a significant nickel laterite prospect towards early production; in addition to holding another 22 identified porphyry copper-gold prospects in the Philippines.

For further information, Contact:

Penny Gould
Executive Vice President
Phone: 780.413.8187

Trent Dahl
Ascenta Capital Partners Inc.
Phone: 604.628.5800
Toll Free: 1.866.684.4209 ext. 228

Richard Mayr
Argentuminvest GmbH
Phone: +49.9421.785250
Fax: +49.9421.785255

The TSX Venture Exchange has not reviewed and does not accept responsibility for the adequacy or accuracy of this release.

This release may contain forward-looking statements including management's assessments of future plans and operations, and expectations of future production. These statements are based on current expectations that involve a number of risks and uncertainties, which could cause actual results to differ materially from those anticipated. These risks include, but are not limited to, the risks associated with the mining and exploration industry (e.g. operational risks in development, exploration and production; delays or changes in plans with respect to exploration or development projects or capital expenditures; the uncertainty of reserve estimates; the uncertainty of estimates and projections relating to production). The assumptions used in the preparation of such statements, although considered reasonable at the time of preparation, may prove to be imprecise and, as such, undue reliance should not be placed on forward-looking statements.

You can view the Next Press Releases item: Thu Jul 19, 2007, Further Drill Results from Kay Tanda

You can view the Previous Press Releases item: Fri Jul 13, 2007, Key Mining Engineers Acquired to Advance Agata Nickel Laterite

You can return to the main Press Releases page, or press the Back button on your browser.