The Cape Bentonite Mine deposits occur in the cretaceous beds in the Southern Cape, South of the Langeberge in the district of Heidelberg.
Originally, it was formed by volcanic ash deposited during the formation of these mountains.
The clay occurs in large beds dipping in a Northerly direction towards the mountains.
All the beds are covered by a fairly soft siliceous sandstone layer, consisting mainly of Cristobalite
The Cape Bentonite deposit is a Sodium-based Bentonite. Sodium Bentonite consists principally of one of the Smectite group of clay and minerals, Montmorillonite being the most common member.
In addition, small amounts of Quartz, Cristobalite, Iron and Titania and minerals occur.
These inert contaminants, making up to 5% of the Bentonite, play no role in the bonding or sealing properties of the product.