Chalcedony (Var: Binghamite)
Cuyuna North Range, Crow Wing County, Minnesota, USA
Large polished specimen of binghamite, with a vein of pale blue agate. The binghamite consists largely of fibrous to platey amphibole altered to a colorful mix of goethite, hematite, quartz, siderite and other minerals. Agate veins such as this are quite rare in binghamite, which itself is best viewed as a jasperoid.
© William S. Cordua