Alternate Names: Mag Carb, MgCO3
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|DENS - Density (Specific Gravity)||3|
|HMOH - Hardness (Moh)||4-4.5|
|SLBY - Solubility||Soluble in warm acids|
Magnesite is used in pottery bodies, glazes, and glass. Magnesite is used in low fire glazes to produce opacity and matteness.
In glaze melts it is an active flux at higher temperatures (2150C+), and it produces elasticity, a lower expansion coefficient and smooth buttery surfaces. At lower temperatures it is a refractory and will matte glazes and make them crawl due to its high shrinkage and contributions to the surface tension of the melt.
This material has a very high Loss on Ignition, this could cause glaze surface issues. Dolomite and talc more readily release their MgO to the glaze melt for a higher temperature glazes.
Magnesium carbonate by itself is very refractory, and is used to make bricks for the cement and metal industries. It is 'dead burned' in rotary kilns, then reground, sized, and dry pressed using organic binders.
This material has a much higher weight density than light magnesium carbonate, the latter is an incredibly fluffy and light white powder.
Glaze Matteness - White Opaque
In low temperature glazes magnesium carbonate in amounts to 15% acts as a refractory, remaining in suspension in the glaze melt to produce a white opaque matte glaze.
Glaze Surface Texture - Crawling
Magnesium carbonate is commonly added to glazes, especially at low fire, to make them crawl (it shrinks and cracks the glaze layer at the low end of firing and then its high melt viscosity pulls the glaze melt into islands). This often produces dramatic visual effects, especially if the crawling glaze color contrasts with the underlying body or slip. Additions vary from 10-30% depending on the host glaze.
Out Bound Links
Calcium Magnesium Carbonate, Raw Limestone
Hydrated Magnesium Carbonate Mineral, Hydromagnesite, Magnesium Carbonate
A magnesium carbonate mineral. It is quarried in California, Washington, Austria, Russia, Manchuria, Greece and Slovakia and processed from sea water. Sources are reasonably consistent in the CO2 cont...
The process of removing the CO2 from magnesite to produce light magnesium carbonate is often called magnesite decarbonization. There is variation in t...
In Bound Links
Magnesium Silicate, Steatite, French Chalk, Hydrated talc