Thin matrix covered in pastel blue chalcanthite from the Bagdad Mine, Yavapai County, Arizona. Natural chalcanthite stable in normal atmosphere is not common. Most calcanthite is lab grown and is moisture sensitive. This attractive thumbnail measures 1 x 1 x 0.5 inches ( 2.5 x 2.5 x 1.3 cm). With minor white calcite(?).