Glaucophane

The Glaucophane mineral is named after two Greek words: glaukos, which means “bluish green”; and phainesthai, which means “to appear.” Specimens can be gray, lavender blue, or bluish black. Crystals are slender, often lathlike prisms, with lengthwise striations. Twinning is common. Glaucophane can also be massive, fibrous, or granular. When iron replaces the magnesium in its structure, it is known as ferroglaucophane. Glaucophane occurs in schists formed by high-pressure metamorphism of sodium-rich sediments at low temperatures (up to 400°F/200°C) or by the introduction of sodium into the process. Glaucophane is often accompanied by jadeite, epidote, almandine, and chlorite. It is one of the minerals that are referred to as asbestos. Glaucophane and its associated minerals are known as the glaucophane metamorphic facies. The presence of these minerals indicates the range of temperatures and pressures under which metamorphism occurs.

Name: From the Greek for bluish green and to appear.

Polymorphism & Series: Forms a series with ferroglaucophane.

Mineral Group: Amphibole (alkali) group: Fe 2+=(Fe 2+ + Mg) < 0.5; Fe 3+=(Fe 3+ + Al vi ) < 0.3; (Na + K)A < 0.5; NaB ¸ 1.34.

Association: Crossite, chlorite, epidote, pumpellyite, lawsonite, omphacite, jadeite, actinolite, barroisite, cummingtonite, aragonite.

Contents

• Chemical Properties of Glaucophane
• Physical Properties of Glaucophane
• Optical Properties of Glaucophane
• Occurrence
• Distribution
• References

Chemical Properties of Glaucophane

Physical Properties of Glaucophane

Optical Properties of Glaucophane

Occurrence

Characteristic of the blueschist facies, in former subduction zones in mountain belts; in the greenschist facies and in eclogites that have undergone retrograde metamorphism.

Distribution

Widespread in some mountain belts. On Syra Island, Cyclades Islands, Greece. At numerous sites in the California Coast Ranges, as on the Tiburon Peninsula and at Vonsen Ranch, Marin Co., at Glaucophane Ridge, Panoche Valley, San Benito Co., and near Valley Ford, Sonoma Co.; in the Kodiak Islands, Alaska, USA. At St. Marcel, Val d’Aosta, and Piollore (Biella), Piedmont, Italy. On Anglesey, Wales. In Japan, at Ubuzan, Aichi Prefecture, and Otakiyama, Tokushima Prefecture.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mindat.org. (2019). Halite: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
• Smith.edu. (2019). Geosciences | Smith College. [online] Available at: https://www.smith.edu/academics/geosciences [Accessed 15 Mar. 2019].