mineral
Ettringite
Ca6Al2(SO4)3(OH)12·26H2O
AI-generated identification · may be incorrectMohs hardness 2-2.5, pale yellow to colorless, vitreous to resinous luster, hexagonal crystal system, perfect cleavage on {1010}.
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Physical properties
Mohs hardness 2-2.5, pale yellow to colorless, vitreous to resinous luster, hexagonal crystal system, perfect cleavage on {1010}.
Formation & geological history
Formed as a secondary mineral in altered limestone, metamorphic marbles, and notably as a hydration product in Portland cement.
Uses & applications
Primarily collected as a rare mineral specimen by enthusiasts; studied extensively for its role in concrete chemistry and degradation.
Geological facts
Ettringite crystals can form rapidly during the setting of high-sulfate cements, sometimes causing structural expansion and cracking.
Field identification & locations
Identified by its pale yellow color, low hardness, and occurrence in association with calcium-rich rocks or altered cements.
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FeO(OH)•nH2O
mineral
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic