Why sandstone and limestone do not show foliation when metamorphosed?
Sandstone and limestone rocks are usually uniform in composition. Also rock made up of all one mineral (e.g. quartz = Quartzite, calcite = Marble; exception = Hornfels) so the minerals do not segregate into layers.
Foliated textures result when the new metamorphic minerals (many of which are platy micas such as Biotite and Muscovite) line up producing a distinct layering in the rock. The layering produces three distinctly different looking rocks; those with slaty cleavage (e.g. Slate), schistosity (e.g. Schist), and mineral banding (or Gneiss Texture). Minerals (e.g., quartz sandstone or limestone), produces rocks that are characterized by fine or coarse interlocking crystals that do not display foliation.
Sandstone and limestone rocks are usually uniform in composition. Also rock made up of all one mineral (e.g. quartz = Quartzite, calcite = Marble; exception = Hornfels) so the minerals do not segregate into layers.
Foliated textures result when the new metamorphic minerals (many of which are platy micas such as Biotite and Muscovite) line up producing a distinct layering in the rock. The layering produces three distinctly different looking rocks; those with slaty cleavage (e.g. Slate), schistosity (e.g. Schist), and mineral banding (or Gneiss Texture). Minerals (e.g., quartz sandstone or limestone), produces rocks that are characterized by fine or coarse interlocking crystals that do not display foliation.
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