Bentonite is a rock composed of clay minerals formed by the alteration of minute glass particles that once composed volcanic ash. The name was derived from the Fort Benton series of Cretaceous rocks in Wyoming where it was first found.

The layers of ash were deposited when extinct volcanoes, in what is now Montana, erupted spewing tons of ash into the air. The volcanic ash was carried by wind and water currents to form numerous beds over most of the interior of North America.

The occurrence of bentonite in the Pembina Mountain area was first reported in 1914. The first recorded claim for bentonite was by Jon E. O’Day on July 18, 1934. From 1936 to 1941, only small amounts of bentonite were quarried.

The main producers during this period were the Spencer brothers of Morden. In 1938, the Morden Bentonite Company Limited was formed but never attained continued production. Pembina Mountain Clays was organized in 1940. A drying plant was built in Morden and an activation plant was built in Winnipeg.

After the bentonite has been mined, it is hauled by truck to the drying plant at Morden. There, the bentonite is dried in kilns and crushed. It is then loaded onto railway cars for the trip to Winnipeg. In the Winnipeg plant the bentonite is further refined and activated with acids. The finished product has a great many uses including:
• a filter to decolourize and remove impurities from animal, vegetable, and petroleum oils, fats and waxes
• reclaiming used oils
• a binding agent in cattle feed
• also used in detergents, cosmetics, as a water softener, as a filter, and for cleaning fur.

Ancient Seas of Manitoba
MordenThe Ice AgeLocal LandformsBentonite

Continental DriftNorth America during the Upper CretaceousShale & Bentonite LayersGeologic Timeline

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Bentonite Exposure
Equipment working on bentonite