noun
MineralogyA mineral of the chlorite group with fan-like crystals, now regarded as a ferroan variety of clinochlore.
Chemical formula: (Mg,Fe,Al)₆(Si,Al)₄O₁₀(OH)₈.
Origin
Mid 19th century; earliest use found in James Dana (1813–1895), geologist, zoologist, and teacher. From French ripidolite or its etymon German Ripidolith from ancient Greek ῥιπίδ-, ῥιπίς fan + German -o- + -lith.
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