Allophane Mineral Data

General Allophane Information

Chemical Formula:

Al2O3•(SiO2)1.3-2•((H2O))2.5-3

Composition:

Molecular Weight = 225.11 gm

Aluminum 23.97 % Al 45.29 % Al₂O₃

Silicon 16.22 % Si 34.70 % SiO₂

Hydrogen 2.24 % H 20.01 % H₂O

Oxygen 57.57 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

(Al₂O₃)(SiO₂)_1.3•2.5(H₂O)

Environment:

In marlstone rocks (TL) and weathering product of volcanic ash.

IMA Status:

Valid Species (Pre-IMA) 1816

Locality:

Grafenthal, Thuringia, Germany Link to MinDat.org Location Data.

Name Origin:

From the Greek allos - "other" and phanos - "to appear" in allusion to its change when blowpiped.

Name Pronunciation:

Allophane + Pronunciation

Synonym:

Ilbaite

Protoallophane

Schrotterite

Allophane Image

Images:

Allophane

Comments: Blue, cuprian, botryoidal allophane on matrix.
Location: Reiche Zeche Mine, Himmelfahrt Mine, Freiberg, Freiberg District, Erzgebirge, Saxony, Germany. Scale: Picture size 5 mm.
© Thomas Witzke / Abraxas-Verlag

Allophane Crystallography

Crystal System:

Amorphous- No Crystals

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

By Intensity(I/I_o): 3.3(1), 2.25(0.2), 1.4(0.1),1.23(0.05), 1.86(0.05),

Physical Properties of Allophane

Cleavage:

None

Color:

White, Green, Blue, Yellow, Brown.

Density:

1.9

Diaphaneity:

Translucent

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Botryoidal - "Grape-like" rounded forms (e.g.. malachite).

Habit:

Encrustations - Forms crust-like aggregates on matrix.

Habit:

Stalactitic - Shaped like pendant columns as stalactites or stalagmites (e.g. calcite).

Hardness:

3 - Calcite

Luminescence:

Fluorescent, Short UV=blue.

Luster:

Waxy

Streak:

white

Optical Properties of Allophane

Gladstone-Dale:

CI meas= -0.087 (Poor) - where the CI = (1-KPDmeas/KC)
KPDmeas= 0.2542,KC= 0.234
Ncalc = 1.44

Optical Data:

Isotropic, n=1.47-1.496.

Calculated Properties of Allophane

Electron Density:

Bulk Density (Electron Density)=1.92 gm/cc
note: Specific Gravity of Allophane =1.90 gm/cc.

Fermion Index:

Fermion Index = 0.0078541141
Boson Index = 0.9921458859

Photoelectric:

PE_Allophane= 1.37 barns/electron
U=PE_Allophane x rElectron Density= 2.64 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Allophane is Not Radioactive

Allophane Classification

Dana Class:

71.01.04.01 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.01)with 1:1 layers

(71.01.04)Allophane group

71.01.04.01 Allophane Al2O3•(SiO2)1.3-2•((H2O))2.5-3 None

71.01.04.02 Hisingerite Fe2Si2O5(OH)4•2(H2O) Unk Mono

71.01.04.03 Imogolite Al2SiO3(OH)4 ? Mono

71.01.04.04 Neotocite (Mn,Fe)SiO3•(H2O)(?) None

71.01.04.05 Zinalsite! Zn2AlSi2O5(OH)4•2(H2O)(?) Mono

Strunz Class:

09.ED.20 09 - SILICATES (Germanates)

09.E - Phyllosilicates

09.ED -Phyllosilicates with kaolinite layers

09.ED.20 Allophane Al2O3•(SiO2)1.3-2•((H2O))2.5-3 None

09.ED.20 Chrysocolla (Cu,Al)2H2Si2O5(OH)4•n(H2O) Unk Ortho

09.ED.20 Neotocite (Mn,Fe)SiO3•(H2O)(?) None

09.ED.20 Imogolite Al2SiO3(OH)4 ? Mono

Other Allophane Information

References:

NAME( Dana8) PHYS. PROP.(Collectors Book of Fluorescent Minerals) OPTIC PROP.(Heinrich65)

See Also:

Links to other databases for Allophane :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - YupRocks

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Ask about Allophane here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

Print or Cut-and-Paste your Allophane Specimen Label here :

Allophane

Al2O3•(SiO2)1.3-2•((H2O))2.5-3
Dana No: 71.01.04.01 Strunz No: 09.ED.20
Locality:

Notes: