San Dimas (Mexico)

Project Overview

The San Dimas mine (“San Dimas”) is owned and operated by Primero Mining Corp. (“Primero”), which purchased the mine from Goldcorp Inc. (“Goldcorp”) in August 2010. The mine is a low-cost producer of gold and silver and has been in continuous production for well over 100 years. The San Dimas gold-silver deposit, located in the San Dimas district on the border of Durango and Sinaloa states, is one of the most significant precious metal deposits in Mexico. The district is comprised of over 100 epithermal bonanza type mineralized gold-silver veins. 

Over the substantial mine life to date, the operating team at San Dimas has demonstrated an exceptional track-record of converting resources into reserves and the mine continues to exhibit excellent exploration upside. Primero believes that it can continue to expand reserves by focusing new drilling programs on areas with significant exploration potential, such as the Sinaloa Graben block, where exploration results confirm mineralization of higher grades and in wider veins than the existing reserves. The current mine life at San Dimas is estimated at over 20 years. 

The San Dimas district has experienced a long mining history dating back to 1757 with the first cyanide mill being built in Mexico at Tayoltita in 1904. Historical production from the district is estimated at 582 million ounces of silver and 11 million ounces of gold, affirming it as a world class epithermal mining province. The mines at San Dimas are underground operations using primarily mechanized cut and fill mining methods. Once milling, cyanidation, precipitation and smelting occur at the San Dimas mill located near the town of Tayoltita, doré bars are poured and then transported to refineries in the United States.

Silver Purchase Agreement

On October 15, 2004, Silver Wheaton entered into a silver purchase agreement with Goldcorp to purchase 100% of the payable silver for a period of 25 years, produced by Goldcorp’s Luismin mining operations in Mexico (owned by Goldcorp at the date of the transaction), which included the San Dimas mine, the Los Filos mine and the San Martin mine, for an upfront payment of C$46 million in cash and 108 million Silver Wheaton Common Shares, plus a payment equal to the lesser of US$3.90 per ounce of delivered silver (subject to an inflationary price adjustment) and the then prevailing market price per ounce of silver.

On March 30, 2006, Silver Wheaton and Goldcorp amended the Luismin silver purchase agreement, eliminating any capital expenditure contributions previously required to be paid by Silver Wheaton. In consideration for these amendments, Silver Wheaton issued to Goldcorp 18 million Common Shares, representing approximately 9.8% of the then outstanding Common Shares, and a US$20 million one year non-interest bearing promissory note, which was paid in full on March 29, 2007.

On August 6, 2010, Silver Wheaton amended the silver purchase agreement relating to the San Dimas mine pursuant to Goldcorp’s sale of the mine to Primero Mining Corp. The term of the silver purchase agreement, as it relates to San Dimas, was extended to the life of mine. During the first four years following closing of the transaction, Primero will deliver to Silver Wheaton a per annum amount equal to the first 3.5 million ounces of payable silver produced at San Dimas and 50% of any excess, plus Silver Wheaton will receive an additional 1.5 million ounces of silver per annum to be delivered by Goldcorp. Beginning in the fifth year after closing, Primero will deliver to the Company a per annum amount equal to the first 6 million ounces of payable silver produced at San Dimas and 50% of any excess. Goldcorp will continue to guarantee the delivery by Primero of all silver produced and owing to the Company until 2029, and a payment of $0.50 per ounce for any shortfall below 215 million cumulative silver ounces delivered to Silver Wheaton by the end of 2031. In addition, Goldcorp will continue to deliver to Silver Wheaton the silver produced by the Los Filos mine. Primero has provided Silver Wheaton with a right of first refusal on any metal stream or similar transaction it enters into.

Reserves and Resources