Definition : Pyrite

Mineral (iron sulphate) sometimes found in the crushed stone serving as backfill under the concrete slab on floor of buildings. By oxidizing in contact with moisture and oxygen, pyrite:

• produces sulfuric acid;
• forms gypsum crystals;
• increases the volume of the crushed stone backfill .

The volume increase of the crushed stone backfill can thus cause a concrete slab on floor to crack and even lift it up.