halloysite — Photo: Artyom Svetlov · CC BY 4.0
Halloysite-7Å
Also known as: Halloysite.
Halloysite-7Å is an IMA-recognized mineral species in the silicate class, with the chemical formula Al₂Si₂O₅(OH)₄.
It crystallizes in the monoclinic crystal system (space group Cm). It is a member of the Clay, Kaolinite structural group.
Key properties: Mohs hardness 2–2.5; typically white or colorless or gray or yellow or brown; white streak; vitreous luster.
IMA symbol Hly-7Å, grandfathered status — known before the IMA’s founding, named in 1826.
Collections: Everyday Minerals.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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