Oriental Minerals Inc.
TSX VENTURE : OTL

Oriental Minerals Inc.

March 17, 2008 08:30 ET

Oriental Minerals Inc.: Updated Resource Estimate of 68 Million Tonnes of O.29% WO3 & 0.05% MoS2 Inferred and 13 Million Tonnes of 0.32% WO3 & 0.06% MoS2 Indicated at Sangdong

VANCOUVER, BRITISH COLUMBIA--(Marketwire - March 17, 2008) - Oriental Minerals Inc. (TSX VENTURE:OTL) is pleased to announce an updated inferred resource of 67.7 million tonnes of 0.29% WO3, and 0.05% MoS2, and an updated indicated resource of 12.7 million tonnes of 0.32% WO3 and 0.06% MoS2 for the Sangdong tungsten-molybdenum deposit in South Korea. The updated estimate represents a 123% increase in tonnes in the indicated category and a 34% increase in inferred tonnes over the initial resource estimate of January 29, 2008.

This updated resource estimate was completed by Wardrop Engineering Inc. in compliance with NI 43-101, and is now based on 42 drill holes completed and analyzed out of an originally planned 87 hole drill program. The previous resource estimate announced January 29th, 2008 was based on 27 drill holes. Both estimates utilized the pre-existing 780 underground drill holes completed by the former operators of the Sangdong mine. Other changes in the updated estimate include the use of a tungsten-oxide-equivalent cut-off grade of 0.10%, compared to a tungsten-oxide-only cutoff grade of 0.15% in the initial estimate. Enhancements have also been made to the geological model based on the addition of the new drilling. A 43-101 compliant Technical Report has been completed and will be posted on SEDAR shortly.

The Sangdong resource is within the skarn zone at the south-eastern end of the deposit which outcrops at surface. Drilling continues at Sangdong, with six rigs currently in operation.

Damien Reynolds, Chairman of Oriental Minerals, noted, "The continued improvement in the size and grade of the Sangdong resource is gratifying, given the additional scrutiny placed on this updated resource estimate. There is still considerable scope to increase resources at Sangdong, however this potential will be pursued in parallel with an aggressive program of engineering, environmental and economic studies. Given Sangdong's status as one of the largest tungsten-molybdenum deposits, the future Preliminary Economic Assessment will assist investors to determine the value of this particular asset. Oriental Minerals will report shortly on other progress within its Uranium, Gold and Base Metals portfolio."

Wardrop Engineering Inc. is now reporting resources using a cut off grade of 0.10% WO3 equivalent. The WO3 equivalent represents a recoverable grade with recoveries of 70% and 80% applied to the tungsten and molybdenum grades, respectively. While kriged interpolation continues to be used in the updated estimate, for this updated estimate Wardrop also capped assays. Aggregate value of tungsten was reduced by 6-15% and molybdenum by 13-21% to compensate for irregular distributions of grade within the database. The metal prices are based on a three year moving average price of US$239 per MTU for the Ammonium Para Tungstate (APT) and US$29.09 per pound for Molybdenum TriOxide. Current price indications for APT are US$254 per MTU and US $33 per pound of Molybdenum TriOxide (source: minormetals.com).



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SANGDONG - INDICATED RESOURCE KRIGED greater than 0.10% WO3 Equivalent
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WO3 eq%
ROCKGROUP TONNES WO3% MOS2% (recoverable)
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LIMESTONE 0
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SKARN 12,658,000 0.32% 0.06% 0.33%
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QUARTZITE 0
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TOTAL INDICATED 12,658,000 0.32% 0.06% 0.33%
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SANGDONG - INFERRED RESOURCE KRIGED greater than 0.10% WO3 Equivalent
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WO3 eq%
ROCKGROUP TONNES WO3% MOS2% (recoverable)
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LIMESTONE 857,000 0.32% 0.04% 0.29%
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SKARN 65,505,000 0.29% 0.05% 0.29%
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QUARTZITE 1,383,000 0.02% 0.11% 0.20%
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TOTAL INFERRED 67,745,000 0.29% 0.05% 0.29%
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Source Wardrop Engineering Inc. Technical Report on the Sangdong
Property Skarn Deposit, March 10, 2008


It is noted that the Quartzite zone appears to be transitional between the tungsten-molybdenum skarn deposit that is the focus of this resource estimate and the deeper, molybdenum deposit referred to as the Deep Moly Deposit.

SANGDONG RESOURCE ESTIMATE METHODOLOGIES

The Sangdong Tungsten mineralization is hosted primarily in tabular calc-silicate horizons in Cambrian-age Myobong Slate (Skarn) associated with bedding concordant and stockworked quartz - carbonate - scheelite veins. Alteration and mineralization is concentrically zoned, diminishing outwards, above a granitic intrusive which induced a higher-grade tungsten molybdenum core.

The deposit was modelled using lithological boundaries, WO3, MoS2 and Bi assay data from both Oriental and 788 historical underground drill holes with Gemcom mining software. Assays were partially capped and samples were composited over 1 metre (m) intervals. A Specific Gravity value of 2.89 g/cm3 was used for the skarn. WO3, MoS2 and Bi grades were interpolated into blocks 20m (strike) x 20m (dip direction) x 5m (vertical) using ordinary kriging.

Oriental drill holes are located on a 100m x 100m north-south orientated grid with a number of infill holes more closely-spaced. Holes are drilled oblique to this grid at azimuths of 135 degrees and 315 degrees. A mix of diamond core and reverse circulation holes (RC) were included, with 31 holes completed as diamond core, size HQ & NQ and 11 holes drilled by RC.

Recoveries of 70% for scheelite and 80% for molybdenum have been estimated based on preliminary mineralogical assessments received from SGS Advanced Mineralogy Facility in Lakefield, Ontario.

The Technical Report and an updated drill plan are available on Oriental Minerals' website at:

http://www.orientalminerals.com/

PRELIMINARY ECONOMIC ASSESSMENT STUDY

Oriental Minerals has appointed Wardrop Engineering Inc. to complete a preliminary economic assessment. The study will examine a likely operating scenario and will determine capital and operating costs for the project and should be completed early in the 3rd quarter of 2008.

CURRENT DRILLING

As at March 13th, 2008 Oriental has completed 16,500m of drilling at Sangdong, with six drill rigs currently in operation.

QUALIFIED PERSON

The Qualified Person who prepared the resource estimate is Mr Gregory Z Mosher, a Senior Geologist with Wardrop Engineering Inc. Mr Mosher visited the property on 2nd and 3rd November 2007 and has over 35 years of relevant experience.

Statements in this news release, other than purely historical information, including statements relating to the Company's future plans and objectives or expected results, constitute Forward-looking statements. Such statements are based on numerous assumptions and are subject to all the risks and uncertainties inherent in the Company's business, including risks related to mineral exploration and development. Consequently, actual results may vary materially from those described in the forward-looking statements.

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

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