Monthly Tech-Tip from Tony Hansen SignUp

No tracking! No ads!

1-9 | A | B | C | D | E | F | Frits | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Turkish Colemanite

Description: calcium borate

Oxide Analysis Formula
CaO 26.50% 0.90
MgO 1.80% 0.09
Na2O 0.10% -
Al2O3 0.10% -
B2O3 41.40% 1.13
SiO2 5.00% 0.16
Fe2O3 0.10% -
SrO 0.70% 0.01
LOI 24.50%n/a
Oxide Weight 144.08
Formula Weight 190.83


The ground colemanite mill is at Bigadic where several colemanite and ulexite mines are located. The production capacity of the mill is 30.000 tpa. The particle size of the product can be adjusted to either -45 or -75 micron depending on demand.
This material is used as a source of B2O3 in many industries, but not commonly in ceramic glazes.

Related Information


Colemanite Data Sheet
URLs - The best place for info on Gerstley Borate
Materials Chilean Ulexite
Materials Turkish Ulexite
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 Colemanite
A natural source of boron that melts at a very low temperature.
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.
By Tony Hansen
Follow me on

Got a Question?

Buy me a coffee and we can talk, All Rights Reserved
Privacy Policy