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Allophane

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Formula:
(Al2O3)(SiO2)1.3-2 · 2.5-3H2O
System:
Amorphous
Colour:
White, pale blue to ...
Lustre:
Waxy
Hardness:
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

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.ED.20

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

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
1 : Sheets of 6-membered rings with 1:1 layers
15.11

15 : Silicates of Aluminum
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Type Occurrence of Allophane

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

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:
(Al2O3)(SiO2)1.3-2 · 2.5-3H2O
Essential elements:
All elements listed in formula:
Common Impurities:
Ti,Fe,Mg,Ca,Na,K

Relationship of Allophane to other Species

9.ED.05DickiteAl2(Si2O5)(OH)4
9.ED.05KaoliniteAl2(Si2O5)(OH)4
9.ED.05NacriteAl2(Si2O5)(OH)4
9.ED.05Odinite(Fe,Mg,Al,Fe,Ti,Mn)2.4((Si,Al)2O5)(OH)4
9.ED.10HalloysiteAl2(Si2O5)(OH)4
9.ED.10HisingeriteFe23+(Si2O5)(OH)4 · 2H2O
9.ED.10Halloysite-7ÅAl2(Si2O5)(OH)4
9.ED.15AmesiteMg2Al(AlSiO5)(OH)4
9.ED.15AntigoriteMg3(Si2O5)(OH)4
9.ED.15Berthierine(Fe2+,Fe3+,Al)3(Si,Al)2O5(OH)4
9.ED.15Brindleyite(Ni,Al)3(Si,Al)2O5(OH)4
9.ED.15Caryopilite(Mn,Mg)3(Si2O5)(OH)4
9.ED.15ChrysotileMg3(Si2O5)(OH)4
9.ED.15CronstedtiteFe22+Fe3+((Si,Fe3+)2O5)(OH)4
9.ED.15Fraipontite(Zn,Al)3((Si,Al)2O5)(OH)4
9.ED.15GreenaliteFe2-3(Si2O5)(OH)4
9.ED.15KellyiteMn22+Al(AlSiO5)(OH)4
9.ED.15LizarditeMg3(Si2O5)(OH)4
9.ED.15ManandoniteLi2Al4(Si2AlB)O10(OH)8
9.ED.15Népouite(Ni,Mg)3(Si2O5)(OH)4
9.ED.15PecoraiteNi3(Si2O5)(OH)4
9.ED.15GuidottiiteMn2Fe3+(Fe3+SiO5)(OH)4
9.ED.20ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O (x < 1)
9.ED.20ImogoliteAl2SiO3(OH)4
9.ED.20Neotocite(Mn,Fe,Mg)SiO3 · H2O
9.ED.25BismutoferriteFe23+Bi(SiO4)2(OH)
9.ED.25ChapmaniteFe23+Sb3+(Si2O5)O3(OH)
15.1AndalusiteAl2(SiO4)O
15.2KyaniteAl2(SiO4)O
15.3SillimaniteAl2(SiO4)O
15.4MulliteAl4+2xSi2-2xO10-x
15.5PyrophylliteAl2(Si4O10)(OH)2
15.6DickiteAl2(Si2O5)(OH)4
15.7NacriteAl2(Si2O5)(OH)4
15.8KaoliniteAl2(Si2O5)(OH)4
15.9Metahalloysite
15.10HalloysiteAl2(Si2O5)(OH)4

Other Names for Allophane

Name in Other Languages:

Other Information

Health Risks:
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

Specimens:
The following Allophane specimens are currently listed for sale on minfind.com.

Localities for Allophane

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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