Metamorphic Minerals

Texture and Microstructure

Metamorphic Rocks

Eclogite

Eclogite: A high P/T metamorphic rock composed of more than 75% vol. garnet (often pyrope or Mg-rich almandine) and omphacite (Na-Ca-Al-Mg clinopyroxene). Both must be present and neither component more than 75% vol. Eclogite never contains plagioclase. Rutile, kyanite, and quartz are typically present.

Discovery and brief history of eclogites

Impressed by the beauty of the metamorphic rock from Saualpe, Austria, René-Just Haüy (father of modern crystallography) created the name "eclogite" (the chosen rock), which he derived from the Greek word εκλογη (choice). The name, eclogite, was used for the first time in 1822 in the second edition of Haüy's famous book, "Traité de mineralogie". The first "scientific" description, however, dates back to the second half of the 18th century, when Horace-Bénédict de Saussure indicated a "beautiful rock that is not described yet" from the Rhone valley in his "Voyages dans les Alpes".

Throughout the 19th century, the origin of eclogite remained an enigma, in spite of great progress in our knowledge of this rock. The first chemical analyses, carried out around 1870, showed that its bulk composition was the same as gabbro. Therefore, eclogite was thought to be either an igneous rock of gabbroic composition or a metamorphosed gabbro. This second hypothesis became preferred when progressive transitions were observed between gabbros and eclogites. In 1903, the Austro-Hungarian petrologist Friedrich Becke (the inventor of the famous "Becke line" method in microscopy) simply by comparing the molar volumes of gabbroic and eclogite parageneses, inferred that eclogite was the high-pressure equivalent of gabbro. In 1920, eclogite was involved in the conception of the metamorphic facies by Eskola. However, a few researchers denied the existence of an eclogite facies, and claimed that high stress instead of high lithostatic pressure could generate eclogites. Finally, In the 20th century, eclogite was definitely considered as a high-pressure metamorphic rock following the development of experimental petrology and the application of thermodynamics. In recent years, the discovery of ultrahigh-pressure (UHP) coesite and diamond-bearing bearing eclogitic rocks in the crust has drastically changed geologists’ ideas concerning the limits of eclogite-facies crustal metamorphism. This generated numerous new research projects with enormous implications for petrology, geodynamics, global tectonics, seismology, and geochemical recycling.

Eclogites classification

During the two last centuries, the survey of eclogite occurrences, first in Europe and then worldwide, has revealed that there are "eclogites and eclogites". Several eclogite classifications were proposed (e.g. Eskola, 1921, 1939; Smulikowski, 1964a; Coleman et al., 1965, Banno, 1970), in which eclogites were discriminated on the basis of their mode of occurrence, mineral and bulk compositions, and geodynamic setting. The classifications of Smulikowski (1964a) and Coleman et al. (1965) are somewhat similar and have proved to be useful. The three eclogite groups proposed by these authors are very different in terms of geodynamics, giving rise to specific hypotheses.

• Group A (eclogites from the mantle): These eclogites are associated with ultrabasic rocks, either in peridotite bodies or as xenoliths in kimberlite pipes. Their origin (mantle melt or subducted oceanic crust) is still debated.
• Group B (eclogites within gneiss): These eclogites are directly related to orogenic metamorphism (Alps, New Zealand and Himalayas). These eclogites forms bands or lenses within migmatite gneissic terrains and are usually surrounded by amphibolite and show retrograde metamorphism.
• Group C (ophiolitic eclogites): They are associated with glaucophanites and, with them, form high-pressure belts in orogens. Since the outset of plate tectonics, they have been considered as remnants of paleo-subduction zones.

Because of their wide range in equilibration T, Carswell (1990) adapted an earlier proposal by S. Banno that subdivides eclogites into three thermal categories:

1. High-T (>900°C). Includes most mantle-derived xenoliths in mafic and ultra-mafic magmatic host rocks.
2. Medium-T (900–550°C). Includes some xenoliths as well as eclogite intercalated with felsic gneisses.
3. Low-T (<550°C). Associated with blueschist-facies rocks in near-trench settings.

Eclogite facies

The eclogite facies was initially recognized in rocks only of basaltic composition, which are transformed at the pressure-temperature conditions of the eclogite facies into spectacular red and green rocks composed of the anhydrous mineral assemblage garnet plus omphacite. The transformation of gabbro (or basaltic rocks) to eclogite may be schematically represented as follows:

[3CaAl₂Si₂O₈ + 2NaAlSi₃O₈] (plagioclase with labradorite composition) + 3Mg₂SiO₄ (olivine) + nCaMgSi₂O₆ (diopside) = [2NaAlSi₂O₆ + nCaMgSi₂O₆] (omphacite) + 3CaMg₂Al₂Si₃O₁₂ (garnet) + 2SiO₂ (quartz)

Despite initially the eclogite facies was initially recognized in rocks only of basaltic composition, it is now known that protoliths other than basalt also can be metamorphosed to pressures and temperatures characteristic of the eclogite facies, and a wide variety of mineral assemblages can be stable at these conditions, including several hydrous mineral phases.

Metapelites: Minerals that have been observed in metapelites include magnesium-rich chloritoid and staurolite, kyanite, garnet, phengite (a muscovite mica with high magnesium and silicon and low aluminum content), chlorite, yoderite and talc. Experimental work shows that pelitic rocks composed primarily of talc and kyanite, which are referred to as whiteschists, can be stable from pressures of approximately 6 kilobars up to greater than 30 kilobars.
Calcareous rocks: Minerals observed in eclogite-facies calcareous rocks include magnesite, dolomite, zoisite or epidote, and omphacite.

The common metamorphic facies. The boundaries between the facies are depicted as wide bands because they are gradational and approximate. P-P = Prehnite-Pumpellyite facies.

Early experimental work on eclogites of basaltic bulk composition suggested that eclogites could generally be stable only if water pressure was much lower than the lithostatic pressure, and the facies was thus thought to represent dry high-pressure metamorphism of basaltic protoliths. Subsequent work on the more diverse protolith compositions revealed, however, that a wide range of water pressures is possible in the eclogite facies and that fluid compositions in equilibrium with the eclogite minerals also probably vary greatly. Eclogite metamorphism is therefore not confined to dry environments but results instead from metamorphism of a variety of rock types at pressures above about 10 kilobars, corresponding to burial to approximately 35 km and at temperatures ranging from about 400 to 1,000 °C. The temperatures of the eclogite facies overlap those of the greenschist, amphibolite, and granulite facies, but the higher pressures result in distinctly different mineral assemblages characterized by high-density mineral phases.

eclogite2020(2).jpg

Eclogite with omphacite (green), garnet (red) and quartz (white). Nordfjord, Western Norway. From Sand atlas.

Eclogite with omphacite (green), garnet (red) and quartz (white). Nordfjord, Western Norway. From Sand atlas.

Eclogite with omphacite (green), garnet (red), quartz (white) and phengite (light brown reflective flakes). Nordfjord, Western Norway. From Sand atlas.

Eclogite with omphacite (green), garnet (red), quartz (white) and kyanite (light blue). Norway. From Virtual microscope.

Eclogite with omphacite (green), garnet (red), quartz (white) and kyanite (light blue). Norway. From Virtual microscope.

Fine-scale layers of eclogite and blueschist showing extensive evidence for ductile deformation. California. From Down to Earth Questions.

Bibliography

• Coleman, R. G., Lee, D. E., Beatty, L. B., & Brannock, W. W. (1965). Eclogites and eclogites: their differences and similarities. Geological Society of America Bulletin, 76(5), 483-508.
• Godard, G. (2001). Eclogites and their geodynamic interpretation: a history. Journal of Geodynamics, 32(1-2), 165-203.
• Jacob, D. E., Viljoen, K. S., & Grassineau, N. (2008, October). Eclogite xenoliths from Kimberley, South Africa–a case study of extensive mantle metasomatism. In International Kimberlite Conference: Extended Abstracts (Vol. 9).
• Kuethe, J.R. (2016). The classification of eclogites and how the role of fluids, mineralogy and chemistry helps to determine their processes of formation.

Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)	Garnet (pink) and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)	Garnet (pink) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic), glaucophane and omphacite in an Eclogite. XPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic), rutile and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)	Garnet (isotropic), rutile and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)
Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Rutile. PPL image, 10x (Field of view = 2mm)	Rutile. PPL image, 10x (Field of view = 2mm)
Garnet (pink) and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)	Garnet (pink) and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)	Garnet (pink) and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)
Garnet (pink), glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)
Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), phengite (rectangular and colorless) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Zoned glaucophane crystals in an eclogite. PPL image, 10x (Field of view = 2mm)	Zoned glaucophane crystals in an eclogite. XPL image, 10x (Field of view = 2mm)
Zoned glaucophane crystals in an eclogite. XPL image, 10x (Field of view = 2mm)	Zoned glaucophane crystals in an eclogite. XPL image, 10x (Field of view = 2mm)	Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 10x (Field of view = 2mm)
Garnet (pink), and omphacite (prismatic, pale-green crystals) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic), and omphacite in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), and omphacite (prismatic, pale-green crystals) in an oclogite. PPL image, 2x (Field of view = 7mm)
Garnet (isotropic), and omphacite in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), and omphacite (prismatic, pale-green crystals) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic), and omphacite in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), phengite (colorless) and omphacite (prismatic, pale-green crystals) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic), phengite (high interference colors) and omphacite in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), phengite (colorless) and omphacite (prismatic, pale-green crystals) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), omphacite (green) and glaucophane (blue) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) and glaucophane (blue) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), omphacite (green) and glaucophane (blue) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (isotropic), omphacite and glaucophane in an eclogite. XPL image, 2x (Field of view = 7mm)	Garnet (pink) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink) and omphacite (green) in an eclogite. XPL image, 2x (Field of view = 7mm)
Garnet (pink), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (pink), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (pink), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (isotropic), rutile, glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)	Garnet (pink, with chlorite alteration), rutile, glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (isotropic, with chlorite alteration), rutile, glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)
Glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)	Glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)
glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)	Glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)
Glaucophane (blue) and omphacite (green) in an eclogite. PPL image, 2x (Field of view = 7mm)	glaucophane and omphacite in an eclogite. XPL image, 2x (Field of view = 7mm)	Garnet (with chlorite alteration), quartz (colorless) and glaucophane in an eclogite. PPL image, 2x (Field of view = 7mm)
Garnet (with chlorite alteration), quartz (gray) and Glaucophane in an Eclogite. XPL image, 2x (Field of view = 7mm)	Garnet (with chlorite alteration), quartz (colorless) and Glaucophane in an Eclogite. PPL image, 2x (Field of view = 7mm)	Garnet (with chlorite alteration), quartz (gray) and glaucophane in an eclogite. XPL image, 2x (Field of view = 7mm)
Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite, garnet (isotropic), rutile and quartz in a eclogite from Bohemia. XPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite, garnet (isotropic), rutile and quartz in a eclogite from Bohemia. XPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite, garnet (isotropic), rutile and quartz in a eclogite from Bohemia. XPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite, garnet (isotropic), rutile and quartz in a eclogite from Bohemia. XPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)	Omphacite (pale green), garnet (pink), rutile (brown) quartz (colorless) in a eclogite from Bohemia. PPL image, 2x (Field of view = 7mm)
Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)	Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)	Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)
Omphacite and garnet in a eclogite. Piani di praglia. Liguria, Italy. XPL image, 2x (Field of view = 7mm)	Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)	Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)
Omphacite (green) and garnet (pink) in a eclogite. Piani di praglia. Liguria, Italy. PPL image, 2x (Field of view = 7mm)	Omphacite and garnet in a eclogite. Piani di praglia. Liguria, Italy. XPL image, 2x (Field of view = 7mm)	Omphacite, opaque minerals and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Omphacite, opaque minerals and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Omphacite, opaque minerals and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Omphacite, glaucophane and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Omphacite, opaque minerals and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Omphacite, opaque minerals and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Omphacite and garnet in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Omphacite, glaucophane and garnet in a clogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Actinolite (green), after omphacite, and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Actinolite (green), after omphacite, and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Actinolite (green), after omphacite, and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	omphacite alterd by green, acicular actinolite crystals and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	omphacite alterd by green, acicular actinolite crystals. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Actinolite (green), after omphacite, and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Actinolite (green), after omphacite, and garnet crystals wit plagioclase + chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)	Actinolite (green), after omphacite, and garnet crystals wit plagioclase+chlorite corona in a eclogite. Lago ortiglieto (Liguria-Piemonte), Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)
Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. XPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)	Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)	Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. XPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. XPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. XPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)	Garnet and glaucophane crystals in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 2x (Field of view = 7mm)
Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)	Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)	Garnet crystal with glaucophane inclusions in a retrograde eclogite. Champdepraz Valle d'Aosta, Italy. PPL image, 10x (Field of view = 2mm)