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Pyrax Pyrophyllite

Oxide Analysis Formula
CaO 0.10% 0.01
K2O 1.81% 0.12
MgO 0.10% 0.02
Na2O 0.30% 0.03
TiO2 0.10% 0.01
Al2O3 16.08% 1.00
SiO2 78.20% 8.25
Fe2O3 0.20% 0.01
Oxide Weight 614.60
Formula Weight 634.26


Pyrax is chemically similar to a clay, it is a hyrated aluminum silicate. But Pyrax has the appearance of a talc. Many properties of Pyrax are quite similar to talcs. Pyrax has a neutral pH and due to the presence of quartz, is highly abrasive.

Density Mg/m3 2.8
pH at 10% solids 6.9
Abrasiveness (Einlehner M/M2 loss, 174,000 revolutions) 450-500

Pyrax is available as types A, B and WA. They vary in particle size and thus bulk density and color.

-325# -10micron -5micron -2.5micron
Pyrax A 90 50 28 13
Pyrax B 95 50 27 11
Pyrax WG 87 44 28 15

Pyrax HS Used mainly in wall tile bodies, especially fast-fire. It lowers firing temperature; produces low moisture expansion bodies; increases thermal shock resistance; and greatly increases firing strength of vitreous bodies. It promotes the development of mullite when substituted for an equivalent amount of feldspar or quartz.

Pyrax RG Refractory grade used in insulating firebrick, metal pouring refractories, ramming mixes, gunning mixes, castable mixes and kiln car refractories.

Related Information


Materials Pyrophyllite
Materials Pyrophyl
Materials Pyrax HS
Typecodes Aluminum Silicate
Materials not classifiable as commonly known aluminum silicates. For example, kaolin is a common aluminum silicate.
Vanderbilt Minerals for Ceramics Technical Sheet
Includes Vansil, Pyrax, Peerless, Dixie, Veegum, Vanzan, Darvan.

By Tony Hansen

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