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Alternate Names: Amtal c98, Amtalc, amtal c 98

Oxide Analysis Formula
K2O 0.30% 0.00
MgO 29.50% 0.92
Al2O3 0.30% 0.00
Fe2O3 0.50% 0.00
CaO 3.50% 0.08
TiO2 0.10% 0.00
SiO2 53.50% 1.12
Oxide Weight 109.96
Formula Weight 124.95


Formerly Pioneer Talc. Subsequently it was manufactured and marketed by Natural Minerals (using the same C-98 name).

AMTAL C-98 was a white-firing talc used as a flux, filler and thermal expansion modifier for traditional, refractory and technical ceramic applications (wall and floor tile, tableware, sanitaryware, electrical Insulators, porcelain, hobbyware ). It is also used in technical ceramics where it functions as the major silicate material replacing clays and feldspars in lower grade alumina products such as steatite ceramics and low-expansion cordierite materials.

AMTAL C-98 was also an economical source of MgO is glazes.

The powder was grey (as opposed to white of many other talcs) because the material contained some amorphous carbon.

Related Information

Texas talc (left) and Montana talc (right)

Texas talc contains some amorphous carbon. The carbon is not stand-alone, but as CO2 in the dolomitic part of the ore. It produces 7% LOI between 750-850C. Even though the color is so much darker in the raw form, it fires whiter!


Materials Talc
Materials Natural Talc C-98
Materials Suzorite 325-PE
Materials Pioneer 2661 Talc
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.
Phlogopite Mica at Wikipedia
Replace Talc with Nepheline Syenite in low temperature white bodies
This is a development project at Plainsman Clays. It is in response to Texas talc no longer being available in North America.
Hazards Talc Hazards Overview
Talc is invaluable in the ceramics industry, it is used as a glaze and body ingredient and as a parting a release agent in various processes. Is it safe?

By Tony Hansen

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