Mineral Factbook

Allophane

Al2O3(SiO2)1.3-2.0·2.5-3.0H2OIMA symbol: Alpgrandfathered

Allophane is a silicate mineral with the formula Al2O3(SiO2)1.3-2.0·2.5-3.0H2O, crystallizing in the amorphous solid system. It has a Mohs hardness of 3, typically colorless, blue, brown or green in color, with a resinous or vitreous luster, a specific gravity of 1.85-1.89. Its streak is red.

Photos

Allophane specimen photo
Mai Seppel · CC BY-SA 4.0 · Commons
Allophane specimen photo
Nessa Eull · CC0 · Commons
Allophane specimen photo
Toma1974 · CC BY-SA 4.0 · Commons
Allophane specimen photo
Modris Baum · Public domain · Commons

Physical properties

Hardness (Mohs)
3single sourceDana, System of Mineralogy, 6th ed. (1892)
Specific gravity
1.85-1.89 g/cm3single sourceDana, System of Mineralogy, 6th ed. (1892)
Color
blue, brown, colorless, green, yellowsingle sourceDana, System of Mineralogy, 6th ed. (1892)
Streak
whitesingle sourceWikidata (CC0)
redsingle sourceDana, System of Mineralogy, 6th ed. (1892)
Luster
resinous, vitreous, waxysingle sourceDana, System of Mineralogy, 6th ed. (1892)

Classification

Nickel-Strunz (10th)9.ED.20Wikidata (CC0)
Nickel-Strunz (9th)9.ED.20Wikidata (CC0)
Dana (8th)71.1.5.1Wikidata (CC0)