Calcium bentonite powder, also known as calcium montmorillonite, is a type of clay mineral that is similar to sodium bentonite but contains calcium ions as the dominant exchangeable cations. Like sodium bentonite, calcium bentonite is formed from volcanic ash deposits and belongs to the smectite group of clays.

Calcium bentonite's ion exchange capacity, absorption characteristics, and swelling properties make it well-suited for certain applications, such as those involving absorption and sealing, where the presence of calcium ions is advantageous.