Scapolite:
Meionite: Ca₄(Al₂Si₂O₈)₃(CO₃,SO₄)
Marialite: Na₄(AlSi₃O₈)₃Cl

Named in 1800 by José Bonifácio de Andrada e Silva from the Greek skapos meaning (a shaft, rod) in allusion to the long prismatic habit of the crystals. Scapolite is a name used for a group of aluminosilicate minerals that includes meionite, marialite and silvialite but the term scapolite generally refers to just the marialite-meionite series, not the full scapolite group, so excludes silvialite. Used as a generic term when the exact chemical composition in the solid solution series has not been determined. Both endmembers of this group form a solid-solution series, similar to the plagioclase group. The pure endmembers do not occur in

It occurs both in igneous and metamorphic environments. It occurs in some granites and nepheline syenites and associated pegmatites; in volcanic rocks it occurs in CO₂ and SO₂ environment as a contact pneumatolytic mineral (Laacher volcanic area, Germany), or by alteration of plagioclase. As a metamorphic mineral it occurs in some siliceous limestones. Scapolite is found in regionally metamorphosed rocks such as marble, gneiss and schist as massive speciems. These massive specimens often exhibit a wood-grain or fibrous texture which facilitates their identification. Well-formed, gem-quality, prismatic crystals with a square cross-section are sometimes found in marbles. In metamorphosed igneous rocks, especially gabbro and basalt, scapolite often occurs as complete or partial replacements of the feldspar grains.

Optical Properties:
• Form: Granular, columnar, stalk-like.
• Cleavage: Good on (100), incross-section the two cleavage planes intersect atright angles.
• Colour: Colourless; inclusions often cause clouding.
• Birefringence: Birefringence increase from marialite to meionite. Marialite has grey interference colours of the I order, and meionite of the II order (bright violet).

Bibliography

• Bucher, K., & Grapes, R. (2011). Petrogenesis of metamorphic rocks. Springer Science & Business Media.
• Fossen, H. (2016). Structural geology. Cambridge University Press.
• Howie, R. A., Zussman, J., & Deer, W. (1992). An introduction to the rock-forming minerals (p. 696). Longman.
• Passchier, Cees W., Trouw, Rudolph A. J: Microtectonics (2005).
• Philpotts, A., & Ague, J. (2009). Principles of igneous and metamorphic petrology. Cambridge University Press.
• Shelley, D. (1993). Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations.
• Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology. Cambridge University Press.
• Vernon, R. H. (2018). A practical guide to rock microstructure. Cambridge university press.

Photo
Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)
Scapolite crystals (II order gray birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)
Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)
Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)
Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)
Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)
Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)
Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)	Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 1x (Field of view = 9mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 1x (Field of view = 9mm)
Colorless, prismatic scapolite crystal and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 2x (Field of view = 7mm)	Scapolite crystal (II order yellow birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 2x (Field of view = 7mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 2x (Field of view = 7mm)
Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 2x (Field of view = 7mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 2x (Field of view = 7mm)	Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 2x (Field of view = 7mm)
Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 2x (Field of view = 7mm)	Colorless, prismatic scapolite crystals and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. PPL image, 2x (Field of view = 7mm)	Scapolite crystals (II order gray-green/blue birefringence) and calcite in a termometamorphic limestone (Angolo limestone). Bazena, Brescia province, Italy. XPL image, 2x (Field of view = 7mm)