Chalcosiderite is a rare mineral, a member of the Turquoise Group and is isostructural with turquoise. This fine, old-time specimen is from Wheal Phoenix in Cornwall, the Type Locality for chalcosiderite. The 3-dimensional, quartz-rich gossan matrix is loaded with vugs richly lined with gemmy, forest-green, grape-like clusters of radial chalcosiderite blades. This is fine material from this historic Cornwall mine and is certainly over 100 years old.