Cronstedtite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameCronstedtite
Chemical FormulaFe²⁺₂Fe³⁺(SiFe³⁺)O₅(OH)₄
Mohs Hardness3.5
Crystal Systemtrigonal
Streak ColorDark greenish black to black
CleavagePerfect on {0001}
FractureUneven
Specific Gravity3.3
Colorsblack, brownish black, dark green
TransparencyOpaque to translucent
Type LocalityWheal Jane (Falmouth Consolidated Mines), Baldhu, Kea, Camborne - Redruth - St Day District, Cornwall, England, UK
Mineral GroupPhyllosilicates
Usescollector's mineral, scientific interest
Associated Mineralsquartz, chlorite, cassiterite, sulfides
Rarityuncommon
Description
A specimen featuring radiating aggregates of dark, almost black, blade-like cronstedtite crystals with a submetallic to vitreous luster, intergrown with translucent, colorless crystals, likely quartz.
Geological Context
Cronstedtite is a hydrothermal mineral typically found in low-temperature veins, often associated with ore deposits of tin and copper, and can also occur in some metamorphic environments.
