1478 Birnessite, Serandite, Leucophanite, Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry; Carriere Mont Saint-Hilaire), Mont Saint-Hilaire, La Vallee-du-Richelieu RCM, Monteregie, Quebec, Canada
Brown-black birnessite pseudomorph after a prismatic 20mm serandite crystal with no matrix attached. The serandite crystallized first, the birnessite replaced the serandite atom-by-atom maintaining the crystal form, but changing the composition. Green crystals are leucophanite....