Dickite Mineral Data

Dickite Mineral Data +

General Dickite Information

Chemical Formula:

Al2Si2O5(OH)4

Composition:

Molecular Weight = 258.16 gm

Aluminum 20.90 % Al 39.50 % Al₂O₃

Silicon 21.76 % Si 46.55 % SiO₂

Hydrogen 1.56 % H 13.96 % H₂O

Oxygen 55.78 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Al₂Si₂O₅(OH)₄

IMA Status:

Valid Species (Pre-IMA) 1930

Locality:

Link to MinDat.org Location Data.

Name Origin:

Named after the Scottish chemist, A. B. Dick.

Dickite Image

Images:

Dickite Ankerite Sphalerite

Comments: White, rhombohedral crystals of ankerite and dark gray, metallic sphalerite on beige dickite.
Location: Prego mine, Kladno, Czech Rebublic. Scale: Picture size 2 cm.
© Dave Barthelmy

Images:

Dickite

Comments: Porcelaneous pure white massive dickite.
Location: Beaver County, Utah, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Dickite Crystallography

Axial Ratios:

a:b:c =0.576:1:1.6135

Cell Dimensions:

a = 5.1375, b = 8.9178, c = 14.389, Z = 4; beta = 96.74° V = 654.68 Den(Calc)= 2.62

Crystal System:

Monoclinic - DomaticH-M Symbol (m) Space Group: Cc

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 3.58(1), 7.15(1), 2.33(0.9),

Crystal Structure:

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Bailey S W , American Mineralogist , 48 (1963) p.1196-1209, Polymorphism of the kaolin minerals

View Additional jPOWD Structure files for Dickite
[1] [2]

Physical Properties of Dickite

Cleavage:

[001] Perfect

Color:

Blue, Colorless, Gray, Yellow brown, White.

Density:

2.6

Diaphaniety:

Subtranslucent to opaque

Fracture:

Earthy - Dull, clay-like fractures with no visible crystalline affinities, (e.g. howlite).

Habit:

Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).

Hardness:

1.5-2 - Talc-Gypsum

Luster:

Pearly

Streak:

white

Optical Properties of Dickite

Gladstone-Dale:

CI meas= 0.042 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.049 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2149,KPDmeas= 0.2166,KC= 0.226

Optical Data:

Biaxial (+), a=1.558-1.562, b=1.56-1.565, g=1.563-1.571, bire=0.0050-0.0090, 2V(Calc)=72-80, 2V(Meas)=52-80. Dispersion none.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Dickite

Electron Density:

r_electron=2.62 gm/cc
note: r_Dickite=2.60 gm/cc.

Fermion Index

Fermion Index = 0.01043
Boson Index = 0.98957

Photoelectric:

PE_Dickite= 1.48 barns/electron
U=PE_Dickite x r_electron= 3.87 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Dickite is Not Radioactive

Dickite Classification

Dana Class:

71.1.1.1 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.1)with 1:1 layers

(71.1.1)Kaolinite group

71.1.1.1 Dickite Al2Si2O5(OH)4 Cc m

71.1.1.2 Kaolinite Al2Si2O5(OH)4 P1 1

71.1.1.3 Nacrite Al2Si2O5(OH)4 Cc m

71.1.1.4 Halloysite Al2Si2O5(OH)4 Cc m

71.1.1.4a Endellite? Al2Si2O5(OH)4·2(H2O) Cc m

71.1.1.5 Odinite (Fe,Mg,Al,Fe,Ti,Mn)2.5(Si,Al)2O5(OH)4 Cm m

Strunz Class:

VIII/H.25-20 VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like with [Si4O10]4- and related groups

VIII/H.25 - Kaolinite group

VIII/H.25-10 Kaolinite Al2Si2O5(OH)4 P1 1

VIII/H.25-20 Dickite Al2Si2O5(OH)4 Cc m

VIII/H.25-30 Nacrite Al2Si2O5(OH)4 Cc m

VIII/H.25-40 Halloysite Al2Si2O5(OH)4 Cc m

Other Dickite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Dickite

Al2Si2O5(OH)4
Dana No: 71.1.1.1 Strunz No: VIII/H.25-20
Locality:

Notes: