Pyrophyillite (Pyrax) is a mica which may not fully melt at Cone 6, but it does interesting things to other glazes.

Digitalfire says Pyrax can replace a feldspar or silica. https://digitalfire.com/material/pyrax+pyrophyllite

I used Tony Hanson's Silky Gloss Clear G1215U, replacing the low-expansion 3249 frit with 3195 and replaced the feldspar with Pyrax.

The result is a milky clear that fires thick with a tendency to crawl, but far less than using the original 3249 frit.

Mix with another glaze 1/3 Pyrax Base Clear and the results can be interesting

Raw Pyrophyillite mica formation before being ground into a powder.