I found a very nice oil spot glaze posted on Facebook by Clara Giorello. She took a cone 10 oilspot glaze, "Daly's oilspot" and changed it to a cone 6 glaze by adding Ulexite. I had not even heard of Ulexite before, so a google search taught me that Ulexite is a sodium borate mineral. It is also known as Sodium Calcium pentaborate octahydrate. It sounds like very cool stuff. It forms complex crystals that refract the light. It is known as "TV Stone." It is similar to Colmenite without the Silica and alumina. Gersley borate has a small amount of it. Clara Giorello ground the mineral herself.
Her recipe is: cone 6
K feldspar 40
Ca Carb 10
add: RIO 10
I tried to find a supplier for Ulexite. I found an import company that was willing to sell me a metric ton of the stuff. Has anyone ever used this and by chance found a distributor?