Figure 20. Close-up of the metamorphic rock shown in Figure 19. These layers were originally sedimentary rock - sandstone and siltstone - that have been converted by heat and pressure inside the earth into metamorphic rock. As metamorphic rocks, the mineral grains have been recrystallized into a microscopic texture somewhat like granite, so that the rock has been hardened. The sedimentary aspect is preserved, however, in the thin layers of different composition.

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Last updated on September 3, 2008

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