Living Up to Its Name: How Hecla Mining keeps Greens Creek green.

• Date: 01 August 2022

Hecla Greens Creek mine is unique in the United States. Located on Admiralty Island near Juneau, it is the only mine in the country allowed to operate inside a federally protected natural monument. Situated in the mountains at the north end of the island, with additional facilities on the northwestern shore, Greens Creek is entirely surrounded by part of the Tongass National Forest known as the Kootznoowoo Wilderness, after the Tlingit name for the island, which means "Fortress of the Bear."

Greens Creek has been in production since 1989 (minus a care and maintenance period from April 1993 through July 1996). It is currently ranked as the tenth largest silver mine in the world. The property includes 440 unpatented lode mining claims, 58 unpatented millsite claims, 17 patented lode claims, and one patented millsite. In addition, the Greens Creek site includes properties under lease from the United States Forest Service (USFS), and it also has title to mineral rights on 7,301 acres of federal land acquired through a land exchange with the USFS where the company is exploring but not mining.

All claims and leases comprise a total of approximately 24 square miles. Greens Creek consists of the mine, an ore concentrating mill, a tailings storage area, a ship-loading facility, camp facilities, a ferry dock, and other related infrastructure.

Digging the Dirt

Miners produce approximately 2,300 tons of ore per day from the underground shaft. From 1989 to 2020, Greens Creek mined 20 million tons. That total output breaks down to 322 million ounces of silver, 2.7 million ounces of gold, 4 billion pounds of zinc, and 1.5 billion pounds of lead.

The primary mining methods are cut and fill and longhole stoping. The Greens Creek ore processing facility includes a SAG/ball mill grinding circuit to grind the run of mine ore to liberate the minerals and produce a slurry suitable for differential flotation of mineral concentrates. A gravity circuit recovers free gold that exists as electrum, a gold/silver alloy in the ore. Gravity concentrates are produced from this circuit prior to flotation. Three concentrates are produced: a silver concentrate which contains most of the silver recovered; a zinc concentrate, which is low in precious metals content; and a zinc-rich precious metals concentrate. A third-party processor turns the concentrate into dore bullion, which can be further refined and sold to precious metal traders. The mine's products are shipped from...