Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate. The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomitic rock type is dolostone.
This sample comes from either the Kicking Horse or Monarch mine near Field in the Yoho National Park near the British Columbia-Alberta border. As well as dolomite, it contains silver-grey galena, pale yellow sphalerite and brassy pyrite. The Kicking Horse mine is on the north side of the Kicking Horse River; the Monarch mine on the south, on the slopes of Mount Stephen. Lead-zinc ore was mined at both mines.
Ore was discovered in 1884 during the construction of the Canadian Pacific Railway when workers noticed the metallic silver galena in talus at the base of Mount Stephen. Several thousand tonnes of ore was mined from the East Monarch outcrop in the cliffs above. The richer but higher and less accessible West Monarch outcrop was discovered in 1917. Around 10,000 tonnes of ore was mined from there between 1917 and 1924, precariously transported down the cliff face via tramway. Mining at Monarch and soon Kicking Horse continued through the 1920s and 1930s. Kicking Horse, originally known as the Black Prince showing, had been discovered around the turn of the century but had low lead grades and so didn’t receive much attention at first.
The ore bodies contain galena (lead ore) and sphalerite (zinc ore) with minor amounts of pyrite and rarely, chalcopyrite. Small amounts of silver were also produced, recovered from the galena. Dolomite is abundant and is the main gangue (waste mineral). The ore bodies are hosted in breccia rock, rock that has been broken up into angular pieces and is held together by a mineral cement. In this case, dolomite rock has been brecciated and is also cemented by intergown dolomite mineral crystals.
In total, around 43,000 tonnes of lead-zinc-silver ore was mined from the Monarch and Kicking Horse mines between 1884 and 1952, when production ceased. Much of the ore was transported to Trail for processing at BC’s largest smelter.
Store: Association for Mineral Exploration (AME)
Accession #: AME 980
Primary Mineral: Dolomite
Site Locality: Kicking Horse and Monarch Mines
Location: Field, British Columbia
Special Features: n/a