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Turkish Ulexite

Description: sodium calcium borate

Oxide Analysis Formula
CaO 19.70% 0.71
MgO 2.00% 0.10
Na2O 5.80% 0.19
B2O3 33.20% 0.96
Al2O3 0.20% -
SiO2 5.20% 0.18
LOI 33.90%n/a
Oxide Weight 133.72
Formula Weight 202.29


This material is imported into North America for use as a flux in the fiberglass industry.

It melts much better than colemanite to a bubble-free transparent clear glass and does so below cone 06. It is very clean and consistent. Its potential in ceramics has not be well explored.

This materials is a candidate in the recipes of materials substituting for Gerstley Borate.

Related Information


Materials Colemanite
A natural source of boron that melts at a very low temperature.
Materials Turkish Colemanite
A mineral with very high B2O3 and CaO content.
Materials Ulexite
A natural source of boron, it melts at a very low temperature to a clear glass.
Materials Hydroboracite 30
Typecodes Flux Source
Materials that source Na2O, K2O, Li2O, CaO, MgO and other fluxes but are not feldspars or frits. Remember that materials can be flux sources but also perform many other roles. For example, talc is a flux in high temperature glazes, but a matting agent in low temperatures ones. It can also be a flux, a filler and an expansion increaser in bodies.
Typecodes Gerstley Borate Substitutes
Many development efforts to create Gerstley Borate substitutes took place during the early 2000s (the initial period when the demise of Gerstley Borate appeared imminent). A number of companies, including Laguna Clays itself, produced and sold these for many years. When Laguna secured another stockpile at the mine and began producing the original material again, interest in substitutes gradually waned. However, the sudden dramatic price increase in 2023 appears to have initiated the process again. Gillespie Borate appears to be the only viable and visible substitute now. Thus, the substitutes listed here are mostly no longer made. Other high-boron materials shown are also no longer available. We continue to recommend sourcing B2O3 from frits instead. Please contact us if you have a specific recipe and we can work with you in your Insight-live account to develop a new recipe that both eliminates the GB and improves overall working and firing properties.
URLs - The best place for info on Gerstley Borate
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