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Blue Mountain District, Marble Township, Garland Co., Arkansas, USA
© 2003 John H. Betts
|System:||Monoclinic||Colour:||White to light brown|
|Hardness:||1 - 2|
|Name:||Named in 1891 by Richard Newman Brackett and John Francis Williams in honor of Colonel Elias William Rector [June 11, 1847 Little Rock, Arkansas,, USA - January 29, 1917 Hot Spring, Arkansas, USA], a politician (Speaker of the Arkansas House of Representatives) and attorney in Hot Springs, Arkansas, who supported the formation of the Arkansas Geological Survey.|
A 1:1 regular interstratification of muscovite/illite (dioctahedral mica) and montmorillonite (dioctahedral smectite). Frequently called "rectorite-K" to distinguish it from regularly interstratified paragonite/montmorillonite = "rectorite-Na".
Classification of Rectorite
|Strunz 8th edition ID:||8/H.18-30|
|Nickel-Strunz 10th (pending) edition ID:||9.EC.60|
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
|Dana 8th edition ID:||220.127.116.11|
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
4 : Sheets of 6-membered rings interlayered 1:1, 2:1, and octahedra
|Hey's CIM Ref.:||16.2.9|
16 : Silicates Containing Aluminum and other Metals
2 : Aluminosilicates of Na
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Type Occurrence of Rectorite
|Type Locality:||Blue Mountain District, Marble Township, Garland Co., Arkansas, USA|
|Year of Discovery:||1891|
Physical Properties of Rectorite
|Colour:||White to light brown|
|Hardness (Mohs):||1 - 2|
Crystallography of Rectorite
|Cell Parameters:||a = 5.13Å, b = 8.88Å, c = 23.85Å|
β = 96.3°
|Ratio:||a:b:c = 0.578 : 1 : 2.686|
|Unit Cell Volume:||V 1,079.91 Å³ (Calculated from Unit Cell)|
Optical Data of Rectorite
|RI values:||nα = 1.519 nβ = 1.550 nγ = 1.559|
|2V:||Measured: 5° to 20°, Calculated: 54°|
|Maximum Birefringence:||δ = 0.040|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Dispersion:||r > v|
Chemical Properties of Rectorite
|Simplified for copy/paste:||(Na,Ca)Al4((Si,Al)8O20)(OH)4·2H2O|
|Essential elements:||Al, H, Na, O, Si|
|All elements listed in formula:||Al, Ca, H, Na, O, Si|
Relationship of Rectorite to other Species
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Rectorite
|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 Rectorite
American Mineralogist (1982): 67: 394-398.
Clays and Clay Minerals: 18: 115-119.
American Mineralogist (1995): 80: 247.
Clay Minerals (1997): 32: 89-95.
Internet Links for Rectorite
Localities for Rectorite
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.
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