# Substituting Ulexite

I'm working on ceramic glaze chemistry. One ingredient I don't have, but want to substitute is ulexite:

$$\ce{NaCaB5O6(OH)6.5H2O}$$

I have borax, calcium borate, and calcium silicate:

$$\ce{NaB4O7 . 10H2O, Ca3(BO3)2, CaSiO3}$$

Since the hydroxides and waters will burn off at firing temperature, it is safe to ignore them. I have already worked out that I can use a mix of the three to supply the needed mount of calcium, boron, and sodium, but I am uncertain of the silicate ions I would be introducing to the mix. I don't know how silicate decomposes at 2200 degrees Fahrenheit. This is important because if it does decompose into silica, it will throw off the balance of silica in the glaze. At such temperatures, iron oxide decomposes to $\ce{FeO}$, so it could make sense that this is possible, but I have no evidence. There isn't much about the decomposition of silicate online, any help?