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Garnet and surrounding matrix from a manganiferous supraophiolitic quartzose schist from ultrahighpressure Lago di Cignana locality, Valtournenche, Italy.

( Pmax >25 kbar, Tmax ca. 600 deg.C. : Reinecke, T. (1991) Very-high pressure metamorphism and uplift of coesite-bearing metasediments from the Zermatt-Saas zone, Western Alps. Eur. J. Mineral., 3, 7-17.))

The matrix assemblage includes quartz (after coesite), phengite (Si ca. 3.4 pfu), Mn-rich phlogopite, piemontite and Mn-rich calcite. Inclusions in this garnet are piemontite and quartz. Note particularly the compositional angular unconformity between core and overgrowth.

For more information about this image contact: Michael L. Williams