Halloysite Mineral Data

Halloysite Mineral Data +

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General Halloysite 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

Environment:

A product of hydrothermal alteration or surface weathering of aluminosilicate minerals, as feldspars. Formed by dehydration of endellite above 110 deg. C.

IMA Status:

Valid Species (Pre-IMA) 1826

Locality:

Angleur, Liµege, Belgium. Link to MinDat.org Location Data.

Name Origin:

Named after Baron Omalius d'Halloy (1707-1789).

Synonym:

Endellite

ICSD 26716

PDF 29-1489

Halloysite Image

Images:

Halloysite Pseudomalachite

Comments: Deep green pseudomalachite crystals on cuprous halloysite.
Location: Black Pine Mine, Philipsburg, Granite Co., Montana, USA. Scale: Crystal size 1-2 mm.
© John Veevaert

Images:

Halloysite

Comments: Pale tan sectile porcelaneous massive halloysite.
Location: Monroe County, Indiana, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Halloysite Crystallography

Axial Ratios:

a:b:c =0.5775:1:1.6741

Cell Dimensions:

a = 5.14, b = 8.9, c = 14.9, Z = 4; beta = 101.9° V = 666.97 Den(Calc)= 2.57

Crystal System:

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

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

By Intensity(I/I_o): 10(1), 4.36(0.7), 3.35(0.4),2.54(0.35), 1.48(0.3), 1.672(0.14), 1.281(0.08),

Physical Properties of Halloysite

Cleavage:

None

Color:

White, Yellowish white, Reddish white, Brownish white, Greenish white.

Density:

2.55 - 2.65, Average = 2.59

Diaphaniety:

Translucent 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:

2 - Gypsum

Luminescence:

None.

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Halloysite

Gladstone-Dale:

CI meas= 0.043 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.031 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2189,KPDmeas= 0.2164,KC= 0.226

Optical Data:

Biaxial (?), a=1.553-1.565, b=1.559-1.569, g=1.56-1.57, bire=0.0050-0.0070

Calculated Properties of Halloysite

Electron Density:

r_electron=2.59 gm/cc
note: r_Halloysite=2.57 gm/cc.

Fermion Index

Fermion Index = 0.01043
Boson Index = 0.98957

Photoelectric:

PE_Halloysite= 1.48 barns/electron
U=PE_Halloysite x r_electron= 3.83 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Halloysite is Not Radioactive

Halloysite Classification

Dana Class:

71.1.1.4 (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.25-40 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 Halloysite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(AntBidBlaNic2) OPTIC PROP.(Mason68)

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Halloysite

Al2Si2O5(OH)4
Dana No: 71.1.1.4 Strunz No: VIII/H.25-40
Locality:

Notes: