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monoclinicuncommonSilicates
Staurolite
(Fe,Mg)2Al9(Si,Al)4O22(OH)2
A small piece of staurolite specimen showcasing its characteristic cross shape, often reddish-brown due to ferrous iron. It typically forms prismatic crystals, frequently twinned into distinctive cross forms.
Staurolite Physical Properties
Mohs Hardness
7Crystal System
monoclinicLuster
vitreousStreak Color
white to grayishCleavage
poor on {010}Fracture
subconchoidal to unevenSpecific Gravity
3.74Colors
reddish-brown, dark brown, yellowish-brown, blackish-brownTransparency
translucent to opaqueType Locality
Brittany (France), Georgia (USA), Virginia (USA), Switzerland, RussiaMineral Group
SilicatesUses
collector, jewelry (rarely)Associated Minerals
garnet, kyanite, sillimanite, andalusite, muscovite, biotite, quartzRarity
uncommonGeological Context
Staurolite is a metamorphic mineral that forms during regional metamorphism of pelitic (clay-rich) rocks under intermediate to high-grade conditions. It serves as an important indicator mineral for specific pressure and temperature ranges in metamorphic terrains.
