Pine Lake Fireclay

Oxide	Analysis	Formula
CaO	0.30%	0.02
K2O	0.50%	0.02
MgO	0.10%	0.01
Na2O	0.30%	0.02
TiO2	1.90%	0.09
Al2O3	27.30%	1.00
SiO2	58.60%	3.64
Fe2O3	1.50%	0.04
LOI	9.50%
Oxide Weight		338.13
Formula Weight		373.63

Notes

This once popular (but variable) fire clay has not been available for many years. It occurs in many clay body recipes and common substitutes are Hawthorn Bond (likely the best) and AP green fire clay. However this is not a refractory material, it has about the same vired maturity at a typical cone 10 brown iron stoneware (or even more vitreous). Porosity is 2% at cone 10R and 10 oxidation. Fired shrinkage is 5.7% at cone 10. At cone 7 porosity is 4% with 5.2 shrinkage. Drying shrinkage is 5.8%, so this is not a highly plastic material like some fireclays (it has about the plasticity of a typical pottery clay).

Very different chemical analyses have been presented for this material.
For example, another lists SiO₂ as 70.8 and Al₂O₃ and 25.4 with no LOI?

Related Information

Lignite can be big trouble

Example of the lignite particles in a fireclay (Pine Lake) that have been exposed on the rim of a vessel after sponging. This is a coarse clay, but if it were incorporated into a recipe of a stoneware, glaze pinholing would be likey.