Cornwall Stone
Also know as: Pegmatite. Graven. Gowen. Manx stone. Meldon stone. Growan. Petunste. Amakusa.
Cornwall stone is a low iron feldspar material used primarily as a flux in clay bodies and glazes. It melts 1150-1300C. It has a more diversified selection of fluxes than other feldspars but also has one of the highest silica contents. By itself it does not melt as well as feldspars (melt flow begins around cone 11 oxidation). It is popular in engobes for its adhesive power during and after firing and in glazes for its low shrinkage and minimal contribution to defects. The blue powdered material is higher in fluorine, the white is calcined and more refractory.
Its diversity of oxides make it similar in composition to common stone, thus its name. It is common to see synthetic substitutes for this material since it is easy to blend other feldspars to approximate the analysis of Cornish stone. These substitutes have the advantage of having no fluorine.
The parent ore materials are much more complex than other feldspars, and tend to be a mix of varying types of igneous rock in different stages of decomposition. Earlier stages of the ore materials are bluer (from fluorine) and contain more fluxes than newer rocks where some of the alkalis and fluorine have been leached and washed away creating a softer material. Cornish stones tend to be classified into major types according to the amount of flux present. Although Cornish stone is quite variable in composition, its low iron makes it an attractive material.
Out Bound Links
- (Materials - Alternative)
Potash Feldspar - K2O.Al2O3.6SiO2
K-Feldspar, Orthoclase, K Feldspar, Potassium Feldspar
- (Materials - Alternative)
Soda Feldspar - Na2O.Al2O3.6SiO2
Na-Feldspar, Na Feldspar, Albite
- (Hazards - General)
Fluorine Gas
Hazards of this material in the ceramic industry a... - (Typecodes)
1: GNM - Generic Material
- (Typecodes)
1: FEL - Feldspar
- (MDT - Member)
UK
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Ron Roy
This is the traditional Ron Roy materials file. He... - (MDT - Member)
North America
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New Zealand
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Crystal Glazes
These materials are specially defined for makers o... - (MDT - Member)
Latin and South America
Latin America and South America. We are working on... - (MDT - Member)
Europe
Countries of Eastern Europe and former Soviet Unio... - (MDT - Member)
Australia
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Asia
All of Asia including Turkey, Russia, Indosnesia, ... - (MDT - Member)
Africa
All of continental Africa. We are working on this ...
In Bound Links
Pictures
Cone 11 flow test of original cornwall stone, H&G substitute 2011 and L3617 calculated equivalent
Example of a calculated Cornwall stone substitute blend (left) vs. Cornwall stone itself. The two are mixed with 20% Ferro Frit 3134 and fired at cone 5.
XML for Import into INSIGHT
<?xml version="1.0" encoding="UTF-8"?>
<material name="Cornwall Stone" descrip="" searchkey="Cornish Stone, China Stone, Corn Stn, China-stone" loi="0.00" casnumber="12168-80-8">
<oxides>
<oxide symbol="CaO" name="Calcium Oxide, Calcia" status="" percent="1.810" tolerance=""/>
<oxide symbol="MgO" name="Magnesium Oxide, Magnesia" status="" percent="0.140" tolerance=""/>
<oxide symbol="K2O" name="Potassium Oxide" status="" percent="4.300" tolerance=""/>
<oxide symbol="Na2O" name="Sodium Oxide, Soda" status="" percent="3.300" tolerance=""/>
<oxide symbol="TiO2" name="Titanium Dioxide, Titania" status="" percent="0.150" tolerance=""/>
<oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="16.330" tolerance=""/>
<oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="73.760" tolerance=""/>
<oxide symbol="Fe2O3" name="Iron Oxide, Ferric Oxide" status="" percent="0.200" tolerance=""/>
</oxides>
</material> | 
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