Rosita D Joint Venture

The Rosita D Joint Venture is a joint venture between Calibre Mining (35%) and Rosita Mining (65%).

The town of Rosita and the Rosita D Joint Venture are located in the Region Autonoma Atlantico Norte (RAAN) province of northeastern Nicaragua, approximately 275km northeast of the capital city of Managua. Rosita is one of the original towns in the historic mining triangle of Nicaragua (Triangulo Minero) which together with Siuna-La Luz and Bonanza have combined to produce more than 5.0 million ounces of gold, 4.0 million ounces of silver and 305 million pounds of copper (Arengi, 2002). The Bonanza Mine located 24 kilometers to the northwest of Rosita is the only mine currently in operation.

The historic Rosita (Santa Rita) open pit copper mine (skarn) is located at the eastern end of the town of Rosita, within the Alder optioned Rosita D concession. The concession covers a 33.6 km2 area and is located in the center of Calibre's eastern Borosi concessions. Formal mining in the Rosita area dates back to 1906 with total historic production from the mine estimated at 305 million pounds of copper, 177,737 ounces of gold, and 2,629,720 ounces of silver from 5,924,572 tons of ore. Average historic grades from the mine were calculated at 2.06% Cu, 0.925 g/t Au, and 15.08 g/t silver (Arengi, 2002). The Rosita D concession is prospective for Cu-Au skarn and porphyry Cu-Au mineralization.

Work completed by Rosita Mining includes trenching, surface sampling, geologic mapping and diamond drilling at five high priority targets (Santa Rita, R13, R13 West, Tipispan and T3). A map of the prospects is shown below. The mineralization is related to mid-Cretaceous or later multi-phase intrusions that lie in contact with the early Cretaceous calcareous host sediments. The mineralized zones show a strong northeast and northwest structural control with grades and widths being higher near structural intersections.

As a result of the exploration work Rosita Mining was able to define a NI43101 Inferred Mineral Resource within the Rosita Stockpiles of 7.95 million tonnes grading 0.62% Cu, 0.46 g/t Au and 9.2 g/t Ag containing 118,500 ounces of gold, 108 million pounds of copper and 2.35 million ounces of silver. Work is ongoing at the Santa Rita, R13, R13 West, Tipispan and T3 prospects with multiple targets ready for additional drill testing.

Recent results from the Rosita D exploration program include: 12.1 metres grading 5.21% Cu, 4.4 g/t Au and 44 g/t Ag (Tipispan); 29.0 metres grading 2.09% Cu, 0.19 g/t Au and 14.6 g/t Ag (T3); 30.0 metres grading 0.8% Cu, 0.31 g/t Au and 14.7 g/t Ag (Santa Rita); 8.0 metres grading 29.54 g/t Au (Santa Rita gold zone). Most recently Alder has outlined a six stage plan that would define a production ready 12-15 million tonne high grade copper-gold resource in the Rosita-D concession by 2016-2017 ( )

View of the Santa Rita Pit looking towards the southeast.
Click to Enlarge

The Rosita Stock Piles resource is based on 55 RC drill holes and 17 vertical channel samples with a cutoff of 0.15% copper equivalent ("CuEq"), and averages 0.62% Cu, 0.46 g/t Au and 9.21 g/t Ag, for a 1.01% CuEq.

The table below lists the NI43-101 Inferred Mineral Resource at the historic Rosita mine (0.15% CuEq cutoff).

Tonnes and Grade Total Contained Metal
Deposit Tonnes Gold Silver Cu Gold Silver Cu
    (g/t) (g/t) (%) (oz) (oz) (lbs)
Rosita Stock Piles 7,950,000 0.46 9.20 0.62 118,000 2.35M 108M

  1. Base case is reported at a 0.15% copper equivalent cut-off grade which incorporates consideration of mining and processing cost, recoveries, commodity prices and selling cost. Estimate assumes a long term copper price of US$2.90/lb, a gold price of US$1,200/oz and a silver price of US$24/oz.
  2. Rounding as required by NI 43-101 reporting guidelines may result in apparent summation differences.
  3. Tonnage and grade measurements are in metric units. Contained gold and silver ounces are reported as troy ounces, contained copper pounds as imperial pounds.
  4. Mineral resources that are not mineral reserves do not have demonstrated economic viability. The estimate of mineral resources may be materially affected by environmental, permitting, legal, title, taxation, sociopolitical, marketing, or other relevant issues.
  5. The quantity and grade of reported inferred mineral resources in this estimation are uncertain in nature and there has been insufficient exploration to define these inferred mineral resources as indicated or measured mineral resources and it is uncertain if further exploration will result in upgrading them to indicated or measured mineral resources.