Chalcosiderite is a rare mineral, a member of the Turquoise Group and is isostructural with turquoise. This showy, old-time specimen features two vugs richly covered with gemmy, forest-green, grape-like clusters of radial chalcosiderite blades on a quartz-rich matrix. This excellent specimen is from historic Cornwall, England and comes with an expertly handwritten, faded label from an older collection. The collection this came out of was a museum stash dating to prior to World War I. Wheal Phoenix in Cornwall is the Type Locality for chalcosiderite.