The company says the modelling methodology that was used led to an error, which will result in around a 50% reduction in the quantity of the previously stated mineral resource estimate.
The mistaken report, authored by Scott E. Wilson Consulting, was effective as of September 10 last year for the project, which is located in Arizona.
The NI 43-101 mineral resource estimate showed 956,800 gold equivalent ounces in the measured and indicated categories, comprised in over 30.8 million tonnes, and 266,340 ounces in the inferred category.
The company said today it is unable to disclose new compliant estimates at this time, but added that preliminary indications are that new estimates will be around 16.2 million tonnes of measured and indicated resources, and around 6.1 million tonnes of inferred resources.
The grades are expected to be in line with the previous report.
The junior mineral explorer said a new technical, restated report will be filed on SEDAR.com as soon as possible, with Scott E. Wilson now recalculating the estimates.
The company has also retained international consulting engineers CDM Smith to confirm the restated estimate, and said that the preliminary economic assessment report for the project is still on track to be released in mid March.
"We are of course disappointed by this unexpected event, however, the current business plan for Phase 1 and Phase 2 of the PEA will proceed as planned," said CEO Dick Whittington.
"We know it is crucial to go forward with reliable and correct data and we are taking appropriate measures to ensure this is done. We continue to be excited by the upside potential of the Moss project."
Earlier this month, Northern Vertex closed the sale of its 51 per cent interest in the Lemhi gold joint venture to Idaho State Gold Company for US$7.65 million, allowing it to focus exclusively on its Moss gold-silver mine in Arizona.
The company is planning to put the Moss project into commercial production by early 2014, with a three phase mine development plan designed to move the project forward from conceptual design and test work to on-site pilot plant testing and then commercial operations.
The phased approach is expected to minimize initial capex and ensure technical and economic objectives are met for subsequent phases prior to proceeding with the plan.
The consulting firm that authored the now-retracted report on the project, Scott E. Wilson, commented in a statement Monday: "We sincerely regret this error. It needs to be emphasized however that the data used in the model is sound and has been checked and verified and the grade estimation is also accurate.
"The distribution of mineralization is good and the geological interpretation is sound. We have verified that the resources that are going to be used in the upcoming PEA pits are correct. All relevant analyses are being done to good industry standards."
Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.