Geological controls on kaolin particle shape and consequences for mineral processing

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doi: 10.1180/000985599546037
Authors:Psyrillos, A.; Howe, J. H.; Manning, D. A. C.; Burley, S. D.
Author Affiliations:Primary:
University of Manchester, Department of Earth Sciences, Manchester, United Kingdom
Other:
China Clays International, United Kingdom
Volume Title:Clay Minerals
Source:Clay Minerals, 34(1), p.193-208. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0009-8558
Publication Date:1999
Note:In English. 48 refs.; illus., incl. 2 tables
Summary:The kaolinized granites of St. Austell, England, are worked to produce a range of china clay products, for some of which the kaolin has to meet stringent particle shape and size specifications. Systematic petrographic study indicates that kaolin occurs in the form of two textural types: (i) finely crystalline kaolin (typically <5 µm in average diameter), which infills dissolution porosity of granitic feldspars, and (ii) coarsely crystalline vermiform aggregates (up to 100 µm or more in length), which are closely associated with expanded micas. The vermiform aggregates are characterized by an intergrowth of mica and kaolin crystals, which can be observed at scales of resolution offered by TEM. Textural and chemical evidence suggest that the expanded mica texture is probably the result of preferential precipitation of kaolin along mica cleavage planes and is not simply a process of chemical replacement. Petrographic examination of kaolin slurries sampled at different points in a typical refinery circuit indicates that platy products with high aspect ratio are derived exclusively from raw materials rich in vermiform aggregates. The fine scale intergrowth of kaolin and mica within the aggregates results in circumstances where mica persists through to fine grained products. Furthermore, the absence of Fe or other chemical components in the kaolin structure suggests that any iron reported for the final products may be a consequence of the presence of Fe-bearing mica within a very fine grained intergrowth.
Sections:Clay minerals
Subsections:Petrology; weathering; soils
Subjects:Clay mineralogy; Clay minerals; Controls; Kaolin deposits; Kaolinite; Kaolinization; Magmatism; Metasomatism; Mineral deposits, genesis; Particles; Sheet silicates; Silicates; Dartmoor; Devon England; England; Europe; Great Britain; United Kingdom; Western Europe; Scilly Isles; Stain Austell England
Coordinates:N502500 N504500 W0034000 W0041500
Abstract Numbers:99M/3564
Record ID:2000001542
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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100 1 |a Psyrillos, A.  |e analytic author  |u University of Manchester, Department of Earth Sciences, Manchester 
245 1 0 |a Geological controls on kaolin particle shape and consequences for mineral processing 
300 |a p. 193-208 
500 |a In English. 48 refs. 
500 |a Abstract number: 99M/3564 
500 |a Category Section: Clay minerals 
500 |a Category Subsection: Petrology; weathering; soils 
500 |a Affiliation: University of Manchester, Department of Earth Sciences; Manchester; GBR; United Kingdom 
500 |a Affiliation: China Clays International; ; GBR; United Kingdom 
500 |a Key title: Clay Minerals 
500 |a Source note: Clay Minerals, 34(1), p.193-208. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0009-8558 
500 |a Publication type: journal article 
504 |b 48 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. 
520 |a The kaolinized granites of St. Austell, England, are worked to produce a range of china clay products, for some of which the kaolin has to meet stringent particle shape and size specifications. Systematic petrographic study indicates that kaolin occurs in the form of two textural types: (i) finely crystalline kaolin (typically #LT5 µm in average diameter), which infills dissolution porosity of granitic feldspars, and (ii) coarsely crystalline vermiform aggregates (up to 100 µm or more in length), which are closely associated with expanded micas. The vermiform aggregates are characterized by an intergrowth of mica and kaolin crystals, which can be observed at scales of resolution offered by TEM. Textural and chemical evidence suggest that the expanded mica texture is probably the result of preferential precipitation of kaolin along mica cleavage planes and is not simply a process of chemical replacement. Petrographic examination of kaolin slurries sampled at different points in a typical refinery circuit indicates that platy products with high aspect ratio are derived exclusively from raw materials rich in vermiform aggregates. The fine scale intergrowth of kaolin and mica within the aggregates results in circumstances where mica persists through to fine grained products. Furthermore, the absence of Fe or other chemical components in the kaolin structure suggests that any iron reported for the final products may be a consequence of the presence of Fe-bearing mica within a very fine grained intergrowth. 
650 7 |a Clay mineralogy  |2 georeft 
650 7 |a Clay minerals  |2 georeft 
650 7 |a Controls  |2 georeft 
650 7 |a Kaolin deposits  |2 georeft 
650 7 |a Kaolinite  |2 georeft 
650 7 |a Kaolinization  |2 georeft 
650 7 |a Magmatism  |2 georeft 
650 7 |a Metasomatism  |2 georeft 
650 7 |a Mineral deposits, genesis  |2 georeft 
650 7 |a Particles  |2 georeft 
650 7 |a Sheet silicates  |2 georeft 
650 7 |a Silicates  |2 georeft 
651 7 |a Dartmoor  |2 georeft 
651 7 |a Devon England  |2 georeft 
651 7 |a England  |2 georeft 
651 7 |a Europe  |2 georeft 
651 7 |a Great Britain  |2 georeft 
651 7 |a United Kingdom  |2 georeft 
651 7 |a Western Europe  |2 georeft 
653 |a Scilly Isles 
653 |a Stain Austell England 
700 1 |a Howe, J. H.,  |e analytic author 
700 1 |a Manning, D. A. C.,  |e analytic author 
700 1 |a Burley, S. D.,  |e analytic author 
773 0 |t Clay Minerals  |d London : Mineralogical Society, Mar. 1999  |x 0009-8558  |y CLMIAF  |n Clay Minerals, 34(1), p.193-208. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0009-8558 Publication type: journal article  |g Vol. 34, no. 1  |h illus., incl. 2 tables 
856 |u urn:doi: 10.1180/000985599546037