Abstract <p>A new practical application is presented for saponite containing waste recovered from the return water suspension of the kimberlite ore beneficiation process in the Arkhangelsk diamond bearing province. A mechanism of mechanochemical transformation of saponite is proposed, consisting of its mechanical activation, high-temperature treatment, and chemical treatment with hydrochloric acid. Based on the developed transformation schemes, it is shown that structural modification of saponite in the saponite-containing material—via a serpentine formation stage followed by high-temperature and hydrochloric acid treatment—allows obtaining an ordered composite structure reinforced with acicular wollastonite particles. Strengthening of the material structure is ensured by interaction between caustic magnesia (MgO) and magnesium chloride (additional modification products), leading to the formation of double salts. This finding opens a promising new direction for the direct use of saponite-containing waste as a raw material for producing cement free structural materials.</p>