Project Overview
The Stillwater (including Stillwater east) and East Boulder mines are underground mining operations, located
near the towns of Nye and McLeod in Montana, US. The mining assets are located on the front range of the
Beartooth Mountains with elevations exceeding 2,700 m above sea level. Stillwater is the only US-based mine
for platinum group metals (“PGM”s) and the largest primary producer of PGMs outside of South Africa and the
Russian Federation.
The Stillwater Complex is a 2.7-billion-year-old layered ultramafic-mafic intrusion that shares common
features with the Bushveld Complex in South Africa. The Stillwater layered intrusion comprises three
distinct zones: i) the Basal series (up to 210 m thick), composed of a chilled, fine-grained gabbro overlain
by gabbro, norite, and feldspar pyroxenites; ii) the Ultramafic series (up to 1,100 m thick), composed of
alternating dunite, chromitite, harzburgite, and bronzite pyroxene; and iii) the Banded series (up to 4,300
m thick), composed of alternating norite, gabbro, and anorthosite.
The Stillwater Mine and East Boulder Mines have been in operation since 1986 and 2002, respectively. The
mines produce from the J-M Reef, located in the lower part of the Banded series, the world’s highest-grade
PGM deposit. The J-M Reef is similar to the Merensky Reef of the Bushveld Complex, but it is 1-3 m
thickness, and contains higher concentrations of platinum and palladium.
Each mine has its own mill and concentrator infrastructure on site. The Columbus metallurgical complex is a
state-of-the-art operation that is capable of providing smelting and refining processes for the mine
concentrates. The complex produces a PGM-rich filter cake that is shipped to a third-party precious metal
refinery.
Stream Details
| Date of Contract |
16-Jul-18 |
| Term |
Life of Mine |
| Stream |
100% of gold and 4.5% of palladium until 375 koz palladium received,
reduced to 2.25%, until 550 koz ounces received, 1% thereafter |
| Upfront Consideration |
$500M |
| Per Unit Production Payment |
18% of spot Au and Pd until reduction of
upfront payment to zero and, 22% of spot thereafter |
| Cost Quartile |
Fourth |
For more information on the Stillwater and East Boulder mines, please visit: www.sibanyestillwater.com (opens in new tab)