Oxford Tripoli Company

Gardeners are familiar with diatomaceous earth because it’s often used as a natural pesticide, but it also has many other uses. Nova Scotia mined a lot of it between 1889-1955.

Diatomaceous earth, also called diatomite, is a mineral formed by the accumulation of the shells of microscopic diatoms, a type of algae that has thrived in many Nova Scotia lakes since the last ice age. Diatoms extract silica from the lake water to make their shells and, when they die, the shells sink to the bottom of the lake and accumulate.

Diatomite shells are essentially pure silica and very small. Each shell has microscopic pores and spine-like protrusions that form a delicate, lace-like structure that is useful in many applications.

Diatomaceous earth is an excellent, nontoxic, insect control agent on creatures such as slugs, ants and even bed bugs, which are killed by crawling over the razor-sharp silica fragments.

It’s also used as a filter in the beverage industry for the clarification of wine, beer and fruit juices, and in water purification systems (liquids can pass through diatomite because it’s porous, but solids are trapped by it). Diatomite is also used as an absorbent because it absorbs six times its dry weight. For example, it’s used to help clean up oil spills.

As a filler, diatomite is used in the tire-making industry and in concrete it makes a stronger, lighter product that is resistant to saltwater erosion. It’s also in pharmaceuticals, paint, cosmetics and art supplies.

You will almost certainly benefit today from the microscopic shells of an algae most people have never heard of!

Mining of diatomaceous earth in Nova Scotia took place in many locations, but most notable were deposits on Digby Neck and in the Cobequid Mountains.

For example, a large deposit in Silica Lake at Castlereagh, Colchester County, was developed by the Oxford Tripoli Company in 1889 and produced 540 tons of dry diatomite per year until 1923 when the deposit was exhausted.

Oxford Tripoli then moved to East New Annan where they produced diatomite from several bogs and small lakes (one of which is also called Silica Lake). This site, shown below, produced 7,700 tons of dry product between 1928 and 1940 when fire destroyed the plant.

Oxford Tripoli sold their product to several markets, including a sugar refinery in Dartmouth, a cable and glass factory in England, and Goodrich and Goodyear Tire in the United States.

To our knowledge, no one has considered mining diatomaceous earth in Nova Scotia for many years even though we still have at least several hundred thousand tons of it in our lakes.

Still, Nova Scotians benefit from it being mined in a dozen other countries. 2.5 million tons of it were extracted in 2019.