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Dickite

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Mas Lavayre, Lodève, Hérault, Languedoc-Roussillon, France
© O. Dziallas

Show Dickite Photos (32)
Formula:
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
System:MonoclinicColour:White, or tinted by ...
Hardness:2 - 2½
Name:Named after Allan Brugh Dick (1833 - 1926), Scottish metallurgical chemist, who first described the species.
Polymorph of:Halloysite, Kaolinite, Nacrite


Kaolinite-Serpentine Group.

A secondary mineral usually of hydrothermal origin in conjuncton with veins, derived in part from the alteration of aluminosilicate minerals; also occurs as an authigenic sedimentary phase.

Classification of Dickite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Explanation of status:Dickite appears to be a polytype of kaolinite (as does nacrite).
Strunz 8th edition ID:8/H.25-20
Nickel-Strunz 10th (pending) edition ID:9.ED.05

9 : SILICATES (Germanates)
E : Phyllosilicates
D : Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets
Dana 7th edition ID:71.1.1.1
Dana 8th edition ID:71.1.1.1

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
1 : Sheets of 6-membered rings with 1:1 layers
Hey's CIM Ref.:15.6

15 : Silicates of Aluminum
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Type Occurrence of Dickite

Type Locality:Pant-y-Gaseg Mine, Amlwch, Isle of Anglesey (Gwynedd; Anglesey), Wales, UK
Year of Discovery:1930

Occurrences of Dickite

Geological Setting:Usually of hydrothermal origin in conjuncton with veins, derived in part from the alteration of aluminosilicate minerals; also occurs as an authigenic sedimentary phase.

Physical Properties of Dickite

Diaphaneity (Transparency):Transparent
Comment:Lustre satiny.
Colour:White, or tinted by impurities
Hardness (Mohs):2 - 2½
Tenacity:Flexible
Cleavage:Perfect
On {001}, perfect.
Density (measured):2.60 g/cm3
Density (calculated):2.62 g/cm3

Crystallography of Dickite

Crystal System:Monoclinic
Class (H-M):m - Domatic
Space Group:Bb {B1 1b} {Cc} {C1c1}
Cell Parameters:a = 5.150Å, b = 8.940Å, c = 14.424Å
β = 96.8°
Ratio:a:b:c = 0.576 : 1 : 1.613
Unit Cell Volume:V 659.42 ų (Calculated from Unit Cell)
Z:4
Morphology:Crystals pseudohexagonal, elongated [100] at times. As aggregates of platelets resembling books. Masses of microscopic crystals.
X-Ray Powder Diffraction:
d-spacingIntensity
For dickite-2M1:(
(
7.15(100)
4.12(70)
3.80(60)
3.58(100)
2.51(50)
2.33(90)
1.975(50)

Optical Data of Dickite

Type:Biaxial (+)
RI values: nα = 1.561 - 1.564 nβ = 1.561 - 1.566 nγ = 1.566 - 1.570
2V:Measured: 50° to 80°, Calculated: 72° to 80°
Maximum Birefringence:δ = 0.005 - 0.006

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Low
Dispersion:none

Chemical Properties of Dickite

Formula:
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
Essential elements:Al, H, O, Si
All elements listed in formula:Al, H, O, Si
Common Impurities:Ti,Fe,Mg,Ca,Na,K

Relationship of Dickite to other Species

Member of:Serpentine Group
Common Associates:
Chalcedony
Related Minerals - Nickel-Strunz Grouping):

- +
9.ED.05Kaolinite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
9.ED.05Nacrite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
9.ED.05Odinite
(Fe,Mg,Al,Fe,Ti,Mn)
 
2.4
(Si,Al)
 
2
O
 
5
(OH)
 
4
9.ED.10Halloysite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
9.ED.10Hisingerite
Fe
3+
2
Si
 
2
O
 
5
(OH)
 
4
·2H
 
2
O
9.ED.10Halloysite-7Å
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
9.ED.15Amesite
Mg
 
2
Al[(OH)
 
4
|AlSiO
 
5
]
9.ED.15Antigorite
(Mg,Fe
2+
 
)
 
3
[(OH)
 
4
|Si
 
2
O
 
5
]
9.ED.15Berthierine
(Fe,Fe,Mg)
 
2-3
(Si,Al)
 
2
O
 
5
(OH)
 
4
9.ED.15Brindleyite
(Ni,Mg,Fe)
 
2
Al(Si,Al)O
 
5
(OH)
 
4
9.ED.15Caryopilite
(Mn,Mg)
 
3
Si
 
2
O
 
5
(OH)
 
4
9.ED.15Chrysotile
Mg
 
3
Si
 
2
O
 
5
(OH)
 
4
9.ED.15Cronstedtite
Fe
2+
2
Fe
3+
 
[(Si,Fe
3+
 
)
 
2
O
 
5
](OH)
 
4
9.ED.15Fraipontite
(Zn,Al)
 
3
[(OH)
 
4
|(Si,Al)
 
2
O
 
5
]
9.ED.15Greenalite
Fe
 
2-3
Si
 
2
O
 
5
(OH)
 
4
9.ED.15Kellyite
Mn
2+
2
Al[(OH)
 
4
|AlSiO
 
5
]
9.ED.15Lizardite
Mg
 
3
[(OH)
 
4
|Si
 
2
O
 
5
]
9.ED.15Manandonite
LiAl
 
4
Si
 
3
BO
 
10
(OH)
 
6
9.ED.15Népouite
(Ni,Mg)
 
3
Si
 
2
O
 
5
(OH)
 
4
9.ED.15Pecoraite
Ni
 
3
[(OH)
 
4
|Si
 
2
O
 
5
]
9.ED.20Allophane
(Al
 
2
O
 
3
)(SiO
 
2
)
 
1.3-2
·2.5-3H
 
2
O
9.ED.20Chrysocolla
(Cu,Al)
 
2
H
 
2
Si
 
2
O
 
5
(OH)
 
4
·nH
 
2
O
9.ED.20Imogolite
Al
 
2
SiO
 
3
(OH)
 
4
9.ED.20Neotocite
(Mn,Fe,Mg)SiO
 
3
·H
 
2
O
9.ED.25Bismutoferrite
Fe
3+
2
Bi[OH|(SiO
 
4
)
 
2
]
9.ED.25Chapmanite
Fe
3+
2
Sb
3+
 
[OH|(SiO
 
4
)
 
2
]
Related Minerals - Hey's Index Grouping:

- +
15.1Andalusite
Al
 
2
[O|SiO
 
4
]
15.2Kyanite
Al
 
2
[O|SiO
 
4
]
15.3Sillimanite
Al
 
2
[O|SiO
 
4
]
15.4Mullite
Al
 
8
[(O,OH,F)|(Si,Al)O
 
4
]
 
4
15.5Pyrophyllite
Al
 
2
Si
 
4
O
 
10
(OH)
 
2
15.7Nacrite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
15.8Kaolinite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
15.9Metahalloysite
15.10Halloysite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
15.11Allophane
(Al
 
2
O
 
3
)(SiO
 
2
)
 
1.3-2
·2.5-3H
 
2
O
Related Minerals - Dana Grouping):

- +
71.1.1.2Kaolinite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
71.1.1.3Nacrite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4
71.1.1.4Halloysite
Al
 
2
Si
 
2
O
 
5
(OH)
 
4

Other Names for Dickite

Synonyms:
Other Languages:
Dutch:Dickiet
German:Dickit
Italian:Dickite
Polish:Dickit
Russian:Диккит
Spanish:Dickita

Other Information

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 Dickite

Reference List:Ross, C.S. and P.F. Kerr (1930) Dickite, a kaolin mineral. American Mineralogist: 15: 34-39.

Grim, R.E. (1953) Clay Mineralogy. McGraw Hill: 370.

Newnham, R.E. (1961) A refinement of the dickite structure and some remarks on polymorphism in kaolin minerals. Mineralogical Magazine: 32: 683-704.

Deer, W.A., R.A. Howie, and J. Zussman (1963) Rock-forming minerals, volume 3, sheet silicates: 194-212.

Sen Gupta, P.K., E.O. Schlemper, W.D. Johns, and F. Ross (1984) Hydrogen positions in dickite. Clays and Clay Minerals, 32, 483-485.

Gaines, Richard V., H. Catherine, W. Skinner, Eugene E. Foord, Brian Mason, Abraham Rosenzweig (1997), Dana's New Mineralogy : The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana: 1407.

Farmer, V.C. (2000) Transverse and longitudinal crystal modes associated with OH stretching vibrations in single crystals of kaolinite and dickite. Spectrochimica Acta: A56: 927-930.

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    Localities for Dickite

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