Blue Glass from Craters of the Moon National Monument, Idaho

Miller, Roy

Blue color, caused by ferric oxide-silicate crust on lava surface, on the 'Blue Dragon' lavas at CRMO (Craters of the Moon National Monument) discussed. Analysis of samples presented Geographic location:CRMO (Craters of the Moon National Monument). A unique, azure-blue lava surface occurs in Craters of the Moon National Monument, Idaho. The scoriaceous structure, glassy luster and sinuous pattern of this 2 mile flow support the local name Blue Dragon. The blue color exists in a 2-3 millimeter, frothy glass layer exposed on the weathered surface. The basalt is abnormally rich in FeO and P2O5. At the time of eruption the magma was probably confined at elevated temperature, in a reducing environment until sufficient lava accumulated to breach subsurface tubes extending horizontally from a cinder core source. The highly fluid lava acquired an immediate surface skin in the form of a black complex ferric oxide-silicate (cronstedite) crust. The sub-crustal, radily cooling lava containing olivine, feldspar and magnetite in a siliceous matrix favored atomic grouping of the form Fe2+ - O-Fe 3+ in the glassy structure. Such ferrous ferrite chromophores create blue color in iron bearing glass according to glass technologists.