Halloysite | |
Chemical Formula |
Al2Si2O5(OH)4 |
Species |
Silicates |
Crystal System |
Monoclinic |
Mohs Scale |
1-2 |
Specific Gravity |
2-2.65 |
Color |
White; grey, green, blue, yellow, red from included impurities. |
Streak |
Paler than the color, or white. |
Luster |
Waxy, Earthy |
Refractive Index |
n = 1.553 - 1.565 n = 1.559 - 1.569 n = 1.560 - 1.570 |
Diaphaneity |
Translucent, Opaque |
Cleavage |
Probable on |
Fracture |
Sub-Conchoidal |
Crystal Habit:Spherical clusters, massive | |
Geological Setting:Halloysite is found in widely varied environments, including as an alteration of basaltic rocks, in hydrothermally altered fissure deposits in monzonites; it is also derived from feldspars, chlorites, micas, rhyolites, granites, volcanic ash, tuffs and pumices. More rarely found in granitic pegmatites, bauxites or laterites, and in some marine and glacial clays. |