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Allophane

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Formula:
(Al
 
2
O
 
3
)(SiO
 
2
)
 
1.3-2
· 2.5-3H
 
2
O
System:AmorphousColour:White, pale blue to ...
Lustre:WaxyHardness:3
Name:From the Greek άλλος ("allos") for "other" or "different" and φαίνεσθαι ("phaenesthai"), "to appear", in allusion to the change it undergoes in a blowpipe flame.


Amorphous hydrous silicate of aluminium, composition not fixed. Principal member of the nominal "Allophane Group."
Copper-bearing varieties can be confused with chrysocolla.
Colourless varieties may be confused with hyalite.

The nano-sized particles have a ball-shaped morphology.

Related to imogolite.

Classification of Allophane

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/H.26-10
Nickel-Strunz 10th (pending) edition ID:9.ED.20

9 : SILICATES (Germanates)
E : Phyllosilicates
D : Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets
Dana 7th edition ID:71.1.5.1
Dana 8th edition ID:71.1.5.1

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
1 : Sheets of 6-membered rings with 1:1 layers
Hey's CIM Ref.:15.11

15 : Silicates of Aluminum
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Type Occurrence of Allophane

Type Locality:Gräfenthal, Thuringian Forest, Thuringia, Germany
Place of Conservation of Type Material:Mining Academy, Freiberg, Germany, 26104.
Year of Discovery:1816

Occurrences of Allophane

Geological Setting:A weathering product of volcanic ash. In hydrothermally altered igneous rocks, from the breakdown of feldspars, and in hydrothermal veins, typically related to copper deposits. In sedimentary rocks, including chalk and coal beds.

Physical Properties of Allophane

Lustre:Waxy
Diaphaneity (Transparency):Transparent, Translucent
Colour:White, pale blue to sky-blue, green, brown
Streak:White
Hardness (Mohs):3
Tenacity:Brittle
Cleavage:None Observed
None
Fracture:Conchoidal

Crystallography of Allophane

Crystal System:Amorphous
Morphology:Rarely observed as ring-shaped particles, with diameters of 50 ºA, which in three dimensions may represent sections through hollow spherules or polyhedra. As hyaline crusts and masses; stalactites and flowstones.

Chemical Properties of Allophane

Formula:
(Al
 
2
O
 
3
)(SiO
 
2
)
 
1.3-2
· 2.5-3H
 
2
O
Simplified for copy/paste:(Al2O3)(SiO2)1.3-2·2.5-3H2O
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 Allophane to other Species

Common Associates:
QuartzCristobaliteImogoliteGibbsiteVermiculite
ChrysocollaLimonite
Related Minerals - Nickel-Strunz Grouping):

- +
9.ED.05Dickite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
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(AlSiO
 
5
)(OH)
 
4
9.ED.15Antigorite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
9.ED.15Berthierine
(Fe
2+
 
,Fe
3+
 
,AlMg)
 
2-3
((Si,Al)
 
2
O
 
5
)(OH)
 
4
9.ED.15Brindleyite
(Ni,Al)
 
3
(Si,Al)
 
2
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
((Si,Al)
 
2
O
 
5
)(OH)
 
4
9.ED.15Greenalite
Fe
 
2-3
(Si
 
2
O
 
5
)(OH)
 
4
9.ED.15Kellyite
Mn
2+
2
Al(AlSiO
 
5
)(OH)
 
4
9.ED.15Lizardite
Mg
 
3
(Si
 
2
O
 
5
)(OH)
 
4
9.ED.15Manandonite
Li
 
2
Al
 
4
(Si
 
2
AlB)O
 
10
(OH)
 
8
9.ED.15Népouite
(Ni,Mg)
 
3
(Si
 
2
O
 
5
)(OH)
 
4
9.ED.15Pecoraite
Ni
 
3
(Si
 
2
O
 
5
)(OH)
 
4
9.ED.15Guidottiite
Mn
 
2
Fe
3+
 
(Fe
3+
 
SiO
 
5
)(OH)
 
4
9.ED.20Chrysocolla
Cu
 
2-x
Al
 
x
(H
 
2-x
Si
 
2
O
 
5
)(OH)
 
4
· nH
 
2
O (x < 1)
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(SiO
 
4
)
 
2
(OH)
9.ED.25Chapmanite
Fe
3+
2
Sb
3+
 
(SiO
 
4
)
 
2
(OH)
Related Minerals - Hey's Index Grouping:

- +
15.1Andalusite
Al
 
2
(SiO
 
4
)O
15.2Kyanite
Al
 
2
(SiO
 
4
)O
15.3Sillimanite
Al
 
2
(SiO
 
4
)O
15.4Mullite
Al
 
4+2x
Si
 
2-2x
O
 
10-x
15.5Pyrophyllite
Al
 
2
(Si
 
4
O
 
10
)(OH)
 
2
15.6Dickite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
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

Other Names for Allophane

Synonyms:
AllophaniteElhuyariteIlbaiteRazoumofskynRazumofskin
RiemaniteRiemannite
Other Languages:
German:Allophan
Allophanit
Elhuyarit
Ilbait
Riemanit
Riemannit
Italian:Allofane
Simplified Chinese:水铝英石
Spanish:Allophanita
Elhuyarita
Ilbaita
Riemanita
Riemannita
Traditional Chinese:水鋁英石
Varieties:
Allophane-evansiteCupro-AllophaneFerriallophanePhosphate-AllophanePlumballophane

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 Allophane

Reference List:

- +
Hausmann, J.F.L. & Stromeyer, F. (1816): Über Silberkupferglanz und Allophan.- Göttingische Gelehrte Anzeigen 2, 1251-1253.

Snetsinger, K.G. (1967): High-alumina allophane as a weathering product of plagioclase. American Mineralogist 52, 254-262.

Kitagawa, Y. (1974): Dehydration of allophane and its structural formula. Amer. Mineral., 59, 1094-1098.

Henmi, T. and K. Wada (1976): Morphology and composition of allophane. Amer. Mineral., 61, 379-390.

Wada, S.I. and K. Wada (1977): Density and structure of allophane. Clay Minerals Bull., 12, 289-298.

Bailey, S.W. (1980): Summary of recommendations of AIPEA nomenclature committee on clay minerals. Amer. Mineral., 65, 1-7.

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: eighth edition. John Wiley and Sons, Inc., 1819 pp.: 1432.(1997).

Internet Links for Allophane

Search Engines:
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  • External Links:
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  • Look for Allophane on Wikipedia
  • Look for Allophane on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Allophane details from Handbook of Mineralogy (PDF)
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  • Allophane specimens for sale - minfind.com
  • Specimens:The following Allophane specimens are currently listed for sale on minfind.com.

    Localities for Allophane

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