Gypsum Overview

Nova Scotia has historically been one of the world’s largest suppliers of gypsum. Gypsum’s main use is as an ingredient in wallboard and most walls in Nova Scotia contain gypsum from the world's largest surface gypsum mine in Milford, Nova Scotia.

327-342 million years ago, global sea levels rose and fell many times. This repeatedly flooded Nova Scotia with what we call the Windsor Sea. Nova Scotia was near the equator at that time so the sea also evaporated repeatedly in the tropical sun.

This process gave us huge gypsum deposits because gypsum forms when water high in calcium and sulfate evaporates, leaving the calcium and sulfate behind as sediment. The sediment builds up and is eventually turned into gypsum rock by heat and pressure.

The lake below is part of the mine that has been reclaimed. "Progressive reclamation" means we reclaim areas where extraction is complete while continuing to mine elsewhere on site.

When gypsum mining started in Nova Scotia in the late 1700s, it was done by farmers who extracted blocks of it from their farms, hauled it by horse and cart to shipping points near Windsor and sold it to local traders. The gypsum was then exported to the east coast of the United States for use as fertilizer.

Gypsum fixes alkaline (high pH) soil. US inventor Ben Franklin learned this from the French and brought the idea to the United States in 1785.

Wallboard (aka drywall) was invented in the United States in 1918. Plaster made from gypsum was sandwiched between two sheets of paper and within ten years, large scale production was revolutionizing the construction industry. This changed the gypsum industry in Nova Scotia as vertically-integrated, international companies brought economies of scale and more advanced equipment to the province. Wallboard also meant that most gypsum would now be used for construction purposes, not fertilizer, although a relatively small amount of Nova Scotia’s gypsum is still used as fertilizer.

Safety is the main reason gypsum is used in wallboard. It contains a significant amount of water at the molecular level and is therefore fire resistant. 100 pounds of gypsum rock contains approximately 21 pounds of water.

Reclaimed area of the Milford mine.