THE MINERAL GLAUCOPHANE



Glaucophane is named from its typical blue color (in Greek glaucophane means "blue appearing"). The blue color is very diagnostic for this species. It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue.

Glaucophane forms a solid solution series with ferroglaucophane; Na2 (Fe, Mg)3Al2Si8O22(OH)2. Glaucophane is the magnesium rich member and ferroglaucophane is the iron rich member. Ferroglaucophane is similar to glaucophane but is denser, generally darker in color with a diminished pearly luster.

Glaucophane is formed typically in a highly metamorphic zone known by the geologic term blueschist facies. This facies forms from material caught under subduction zones in mountain belt regions. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. Its glaucophane's color that gives this facies its name. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.

PHYSICAL CHARACTERISTICS:

 

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