Bornite is an important copper ore mineral found in many different types of copper deposit. It is also known as peacock ore because of its iridescent purple-blue-green tarnish. Fresh bornite, however, is copper red. Bornite commonly occurs with other copper sulphide minerals such as chalcocite and weathers, or “oxidizes”, to malachite.
Chalcopyrite is the most common ore mineral for copper and is a sulphide of iron and copper. Chalco comes from the Greek word chalko, meaning copper. Chalcopyrite is commonly found in sulphide deposits in most ore-forming environments. A characteristic deep brass yellow colour and iridescent green-to-purple weathering surfaces distinguish chalcopyrite from gold and sulphides such as pyrite.
This sample comes from the Bethlehem copper porphyry deposit in the Central Interior. The deposit is about 15 km west of the small town of Logan Lake, and about 80 km southwest of Kamloops.
The Bethlehem deposit is one of the deposits that make up the Highland Valley Copper mine, which also includes the Lornex, Highmont and Valley deposits. Early prospectors found copper mineralization in the Highland Valley area in the late 1800s and started hand mining at the Snowstorm and Iona zones of the Bethlehem deposit in 1907, when a wagon trail was built to nearby Ashcroft and the Fraser Canyon railway line. Large-scale open pit mining started at Bethlehem in 1962 and continued until the early 1980s, when production shifted to the other deposits, which are still being mined today. The large Valley pit and operations are visible from a lookout on Highway 97C.
The main ore minerals at the Bethlehem deposit were bornite and chalcopyrite, as seen in this sample. The ore minerals are mainly in very narrow veins, often only a few millimetres wide. Chalcopyrite is also found as fine “disseminations”, or speckles, throughout the host granodiorite rock. Pyrite is also common at Bethlehem, mainly towards the outer edges of the deposit. The other ore mineral mined at Bethlehem was molybdenite, another sulphide mineral and the main ore for molybdenum, which also occurs in narrow veins with quartz.
From 1962 to 1982, production at the Bethlehem mine totalled 96,324,510 tonnes of ore that yielded 99,826,893 grams silver, 1,279,833 grams gold, 398,112,545 kilograms copper and 851,048 kilograms molybdenum.
Store: Association for Mineral Exploration
Accession #: AME 9
Primary Mineral: Bornite-Chalcopyrite
Site Locality: Bethlehem Mine
Location: Highland Valley, British Columbia
Special Features: n/a