London—Target Resources, an alluvial diamond and gold mining company that operates in Sierra Leone, announced on Monday a $5 million exclusive marketing agreement for its stones with Tiffany and Co.

The investment will be in the form of a five-year subordinated debt. Tiffany will have first right of refusal on Target's production at market price and can sell, on Target's behalf, diamonds it does not wish to keep for its own use.

Completion of the investment is subject to final documentation.

"This investment in Target is consistent with our policy of selectively investing in diamond miners who ethically mine high-quality stones," Tiffany Chief Financial Officer James Fernandez said in a statement. "Sierra Leone is a well-known source of high-quality rough stones, and Target's production to date has been encouraging."

Fernandez also noted that Tiffany has followed Target for some time and is impressed by its commitment to high corporate social responsibility and environmental standards.

Sierra Leone was the setting of last year's film Blood Diamond, which portrayed the illicit diamond trade during the country's civil war in the late 1990s. The country is now at peace, though both the diamond industry and human rights organizations are still working to improve conditions for alluvial miners there.

Freddy Hager, chairman of Target, said he was pleased by the deal with Tiffany.

"We are delighted to receive this vote of confidence both in the quality of our stones and in the way we mine them from what is arguably the world's most prestigious diamond retailer," he said.