Bentonite (Montmorillonite Clay)

Bentonite is a soft, absorbent clay whose principal mineral is montmorillonite, a layered aluminosilicate of the smectite group. In car care it is the material behind clay bars and clay mitts: the clay grabs and pulls bonded surface contamination (rail dust, overspray, industrial fallout) off the clear coat as the bar glides across a lubricated panel. It also appears as a rheology modifier and thickener in some pastes, polishes, and gels.

Health: Bentonite and montmorillonite have no GHS hazard classification as supplied and are not listed under California Prop 65. The clay itself is benign to skin and eye contact. The one documented concern is long-term occupational inhalation of dry clay dust. Some natural bentonite contains a minor amount of crystalline silica (quartz), which is separately Prop 65-listed and classified by IARC as a Group 1 carcinogen when inhaled as a respirable dust. That risk pertains to mining and dry-powder handling, not to the moist, bound clay form found in detailing clay bars and mitts.

Environment: Bentonite is an inert, naturally mined mineral with negligible environmental impact at car-care volumes. It is not aquatically toxic, not bioaccumulative, and not persistent in the regulatory sense.