Twin Metals Minnesota LLC is the joint venture company between Duluth Metals Limited (60% ownership interest) and Antofagasta plc (40% ownership interest). In 2011, Twin Metals Minnesota LLC acquired Franconia Minerals Corporation. Franconia`s principal assets are a 70% interest in the Birch Lake, "old Maturi" (not including former Nokomis property) and Spruce Road deposits through the Birch Lake Joint Venture, with Beaver Bay Resources owning the remaining 30%. Franconia announced in November, 2010 its intention to increase its ownership at the Birch Lake Joint Venture to 82% upon commencement of production. All of the forgoing Indicated and Inferred Mineral Resources are expressed as a 100% ownership position. Exploration Target tonnages reflect TMM's current 70% interest in a portion of these properties, which will increase to 82% upon production.
The Mineral Resource Estimate discussed in the Technical Report incorporates assay data from 266 holes totalling 871,000 feet drilled on the Maturi deposit between 2006 and 2011, in addition to information from 99 legacy holes also in the geologic data base. The Birch Lake deposit resource estimate incorporates assay data from 65 holes totalling 155,000 feet drilled between 2000 and 2010, and information from an additional 14 legacy holes. The Spruce Road deposit resource estimate incorporates assay data from 210 legacy holes. The effective date of the mineral resource estimate is April 23, 2012.
The new Mineral Resource estimate represents an increase in tonnage and metal over what was used in Duluth Metal's Preliminary Economic Assessment (PEA) of January 8, 2009. The current Prefeasibility Study that is underway will review the scale, timing, and development of the Twin Metals Minnesota Project such that the information is appropriate to this latest estimate; additional modifications to some assumptions in the current Prefeasibility Study are likely when the results of the planned Fall 2012 update to the Mineral Resource estimates are available. The January 8, 2009 PEA report should be considered no longer relevant to the Twin Metals Minnesota Project.
A map showing the boundaries of the areas for which Indicated and Inferred Mineral Resources have been estimated and the Exploration Target Areas can be found as part of this press release, and is posted on the Company website at http://www.duluthmetals.com.The Mineral Resource estimates in the Technical Report for the Maturi, Birch Lake and Spruce deposits are based on a 0.3% copper cut-off grade to define the resource model. Based on AMEC`s review of metal prices, process recoveries, refining costs and underground mine operating costs likely to apply at the Twin Metals site, the 0.3% copper cut-off grade (highlighted) is considered the base case for the statement of Indicated and Inferred Mineral Resources at this time.