The whitest test bar here is a New-Zealand-kaolin-based cone 6 porcelain (NZK). NZK has low plasticity, so this body employs VeeGum to improve it. Immediately to the left of it are three North American-koalin-based bodies using standard bentonites. The bar to its right is a Grolleg-based body that uses a standard bentonite rather than a white burning one. All are plastic.
A clay deposit that is near the site of erosion and alteration. They have more mechanical impurities and fewer chemical and mineralogical impurities. Primary clays have larger particles and less plasticity.
New Zealand Halloysite
The whitest burning kaolin we have ever seen. It is very sticky when wet, suspends glazes well & makes super white porcelain (with help from a white bentonite).