This is Alberta Slip (GA6C) on the left. Added frit is melting the Alberta Slip clay to it flows well at cone 6 and added rutile is creating the blue variegated effect (in the absence of expensive cobalt). However GA6D (right) is the same glaze with added Tin Oxide. The tin completely immobilizes the rutile blue effect, it brings out the color of the iron (from the rutile and the body).
GA6-D - Alberta Slip Glossy Brown Cone 6
Plainsman Cone 6 Alberta Slip based glaze. It can be found among others at http://albertaslip.com.
GA6-C - Alberta Slip Rutile Blue Cone 6
Plainsman Cone 6 Alberta Slip based glaze the fires bright blue but with zero cobalt.
A type of ceramic glaze in which the surface variegates and crystallizes (on cooling) from the presence of rutile mineral in the recipe.