Azurite forms by the weathering of other copper minerals. Copper ore minerals like chalcocite and bornite “rust” when they come into contact with oxygen in the air or groundwater. This causes their atomic structure to change to become brightly coloured azurite. Azurite is often found at the surface above buried copper deposits and is a useful clue for prospectors and geologists looking for new deposits.
Malachite is a green hydrous copper carbonate mineral that forms near the Earth’s surface as other copper ore minerals, like bornite, are exposed to the atmosphere and weather, or oxidize. Malachite often forms as coatings on joints and fractures or in rock cavities. It often occurs in banded “botryoidal” masses. Botryoidal means is has an appearance similar to a bunch of grapes. Malachite commonly occurs with azurite, another secondary copper mineral that forms by weathering copper sulphides. Together, they are clues that more extensive copper mineralization might be nearby.
This sample is from near Hedley in the Southern Interior of BC. The area is known for its gold skarn type of mineral deposits.
Several gold deposits have been developed and mined within a few kilometers of Hedley. The area’s volcanic rocks and sediments, including limestones, are good hosts to mineral deposits. Younger igneous rocks intruded the older host rocks, percolating through the limestones and reacting with them to precipitate gold and sulphide minerals like chalcopyrite (copper ore), pyrite (Fool’s gold), pyrrhotite (iron sulphide), sphalerite (zinc ore) and magnetite (iron oxide). Garnet is also commonly found in gold skarn deposits.
We don’t know exactly where this sample came from, but we do know that it probably helped early prospectors locate the deposits that were mined. It contains azurite and malachite, two minerals often found at the surface near buried copper deposits. Maybe it helped the first prospectors discover the Nickel Plate mine in 1898.
Four main mines produced gold, silver and copper in the area between 1904 and 1955, with smaller scale mining continuing into the 1990s. The French and Goodhope gold mines were located about 5 km southeast of Hedley; the Nickel Plate and Hedley Mascot mines about 3 km northeast. The entrance to the Nickel Plate and Hedley Mascot underground workings can still be seen perched high on the steep mountainside north of Hwy 3. Although they were mined as two separate deposits, several underground tunnels connected them during their mine life.
Between 1904 and 1996, 14,604,948 tonnes of ore were mined, producing 15,941,519 grams of silver, 66,166,980 grams of gold, 981,030 kilograms of copper and 4 kilograms of zinc
Store: Association for Mineral Exploration (AME)
Accession #: AME 153
Primary Mineral: Azurite-Malachite
Site Locality: n/a
Location: Hedley, British Columbia
Special Features: n/a