Distribuzione dello stilpnomelano nel Paleozoico del Brianzonese ligure
Over two thousand thin sections of crystalline, igneous, volcanic and sedimentary epimetamorphic rocks from the paleozoic basement of the ligurian Briançonnais have been examined. About 2% of them contain needles, flakes, and sheaf-like aggregates; their pleochroism ranges from brown to yellowish in most cases (ferri-stilpnomelane, always associated with K-feldspar bearing rocks and often growing on K-feldspar crystals), or, more rarely, from green to yellow-greenish or colorless (ferro-stilpnomelane,...