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Chatham Co., North Carolina, USA
© Norman King
Note: halloysite-7Å is NOT a polytype of halloysite.
It is an approved (grandfathered) species distinct from Halloysite-10Å.
A synonym is "metahalloysite."
See also the chemically identical kaolinite.
Classification of Halloysite-7Å
|IMA status:||Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"|
|Nickel-Strunz 10th (pending) edition ID:||9.ED.10|
9 : SILICATES (Germanates)
E : Phyllosilicates
D : Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets
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Type Occurrence of Halloysite-7Å
|Type Locality:||Angleur, Liège, Liège Province, Belgium|
Crystallography of Halloysite-7Å
|Class (H-M):||m - Domatic|
|Cell Parameters:||a = 5.14Å, b = 8.9Å, c = 14.9Å|
β = 101.9°
|Ratio:||a:b:c = 0.578 : 1 : 1.674|
|Unit Cell Volume:||V 666.97 Å³ (Calculated from Unit Cell)|
|Comment:||Space group Cc.|
Chemical Properties of Halloysite-7Å
|Simplified for copy/paste:||Al2(Si2O5)(OH)4|
|Essential elements:||Al, H, O, Si|
|All elements listed in formula:||Al, H, O, Si|
Relationship of Halloysite-7Å to other Species
|Related Minerals - Nickel-Strunz Grouping):|
Other Names for Halloysite-7Å
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Halloysite-7Å
American Mineralogist 39 (1954), 97
American Mineralogist 40 (1955), 1110
Acta Crystallographica B31 (1975), 2851
Clays and Clay Minerals 26 (1978), 25
Powder Diffraction 4 (1989), 19
Clays and Clay Minerals (1991): 39: 113.
Handbook of Mineralogy (Anthony et al.), 2 (1995), 311
Internet Links for Halloysite-7Å
Localities for Halloysite-7Å
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.