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Kyanite
Sillimanite Mineral of theoretical formula Al2O3:SiO2
Chemistry
Chemistry available on new site, see link above
Links to Other Materials
- Virginia Kyanite -
- Andalusite - Related
- Sillimanite - Related
- Sillimanite - Related
- Cache
Miscellaneous
- Family: Refractory
- Region: North America
- Mined At: Unspecified
- Raw Mineral: Yes
- Generic: Yes
Notes
Kyanite is a super-duty refractory material with very high resistance to thermal shock. It is widely employed in body formulations used in porcelain, tile bodies, and casting mixes. The material reduces fired shrinkage, increases mechanical strength and thermal shock resistance and allows products to be made with thinner walls, better resistance to dunting, deformation and chipping. Kyanite's long jagged particles tend to form an interlocking no-shrink crystal matrix (like a felt) in bodies fired to low heat (potters use it up to 30% in raku bodies).
Kyanite is used in both refractories and ceramics, large grain sizes making an excellent high temperature grog. It is volume stable and has excellent hot load strength.
Because of its expansion characteristics it makes an excellent crack filler.
Kyanite melts at about cone 36-38. This refractory character makes it useful in insulating brick, kiln furniture, refractory shapes, etc.
No material has the theoretical 1:1 Al2O3:SiO2 chemistry, we have shown an average chemistry for Virginia Kyanite.
It is a refractory aluminum silicate mineral found in large deposits in India, Africa and the USA. American kyanite occurs in association with quartz, from which it must be mechanically separated by grinding. Indian kyanite is processed from surface boulders, and can be calcined in lump form and graded in coarser sizes. American kyanite is the most consistent, Indian the most pure, African the least consistent in quality.
Kyanite is available in varying grain sizes down to 325 mesh and in calcined-to-mullite form. The decomposed mullite form is volume-stable with temperature increase, while the raw form of kyanite displays definite expansion during heatup. Depending on grain size, this phenomenon permits the use of kyanite in clay formulations to counteract the shrinkage of the clay body during firing (see also Spodumene). Kyanite has proven invaluable in cements, ramming mixes, and mortars for this purpose.
During calcining pure kyanite decomposes at into mullite and silica at 2750F with associated specific gravity change from 3.6 to about 3.0.
Properties
Body Thermal Expansion -
Kyanite is a super-duty refractory material with very high resistance to thermal shock.
Data
- Specific Gravity: 3.00
- Melting Point (MP): CONE 37
- Melting Point (MP): CONE 37
- Specific Gravity: 3.00
URLs
- Wikipedia Definition - http://en.wikipedia.org/wiki/Kyanite
Suppliers
- Generic
Authors
- Tony Hansen (Owner)
XML
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