Glaucophane

Description

A double chain silicate (amphibole) type mineral that typically occurs as blue-gray sheets. Glaucophane is found in dense metamorphic rocks, such as basalts. Significant deposits have been discovered in Greece (Cyclades Islands, Syra Island), Italy (St. Marcel, Val d'Aosta, Piollore), Wales (Anglesey), Australia, Japan, and the US (Kodiak Islands, California). The pleochroic mineral changes colors from yellow to violet to blue when a thin section is viewed in plane polarized light.

Synonyms and Related Terms

blue schist; blueschist

FTIR (PMA)

Physical and Chemical Properties

• Crystal system=monoclinic (fibrous, granular, or massive)
• Cleavage=good in two directions (56 and 124 degrees).
• Fracture=brittle, conchoidal
• Luster=vitreous to pearly
• Streak=grayish blue
• Nonfluorescent
• Pleochroic=from yellow to violet to blue-green
• Composition = Na2(Mg3Al2)Si8O22(OH)2
• Mohs Hardness = 6.0-6.5
• Density = 3.00-3.15

Resources and Citations

• WebMinerals at http://webmineral.com/data/Glaucophane.shtml (Accessed Jan. 6, 2006) hardness=6.0-6.5, density =3-3.15

• McGraw-Hill Access Science at http://www.accessscience.com/Encyclopedia/2/29/Est_291100_frameset.html?doi (Accessed Jan. 6, 2006)

• Geology.about.com at http://geology.about.com/library/bl/images/blglaucophane.htm (Accessed Jan. 6, 2006)

• Mineral Galleries at http://www.galleries.com/minerals/silicate/glaucoph/glaucoph.htm (Accessed Jan. 6, 2006) hardness=5-6, density = 3-3.2