{"thcode":4,"term":{"code":"5","name":"Metamorphic rock","parent":"0","scope":"A rock derived from pre-existing rocks by mineralogical, chemical, and\/or structural changes, essentially in the solid state, in response to marked changes in temperature, pressure, shearing stress, and chemical environment, generally at depth in the earth's crust."},"uf":[],"bt":[{"code":"0","name":"Earth material","parent":null,"scope":"Geologic map unit classification (Bruce R. Johnson) version 6.2: A hierarchical classification of earth materials for digital geologic maps."}],"nt":[{"code":"5.8","name":"Amphibolite","parent":"5","scope":"A crystalloblastic rock consisting mainly of amphibole and plagioclase with little or no quartz."},{"code":"5.13","name":"Calc-silicate rock","parent":"5","scope":"A metamorphic rock consisting mainly of calcium-bearing silicates such as diopside and wollastonite, and formed by metamorphism of impure limestone or dolomite."},{"code":"5.10","name":"Eclogite","parent":"5","scope":"A granular rock composed essentially of garnet (almandine-pyrope) and sodic pyroxene (omphacite)."},{"code":"5.7","name":"Gneiss","parent":"5","scope":"A foliated rock formed by regional metamorphism, in which bands or lenticles of granular minerals alternate with bands or lenticles in which minerals having flaky or elongate prismatic habits predominate. Generally less than 50% of the minerals show preferred orientation."},{"code":"5.6","name":"Granofels","parent":"5","scope":"A medium- to coarse-grained granoblastic metamorphic rock with little or no foliation or lineation."},{"code":"5.9","name":"Granulite","parent":"5","scope":"A metamorphic rock consisting of even-sized, interlocking mineral grains less than 10% of which have any obvious preferred orientation."},{"code":"5.11","name":"Greisen","parent":"5","scope":"A pneumatolytically altered granitic rock composed largely of quartz, mica, and topaz."},{"code":"5.1","name":"Hornfels","parent":"5","scope":"A fine-grained rock composed of a mosaic of equidimensional grains without preferred orientation and typically formed by contact metamorphism."},{"code":"5.2","name":"Metasedimentary rock","parent":"5","scope":"A sedimentary rock that shows evidence of having been subjected to metamorphism."},{"code":"5.3","name":"Metavolcanic rock","parent":"5","scope":"A volcanic rock that shows evidence of having been subjected to metamorphism."},{"code":"5.4","name":"Phyllite","parent":"5","scope":"A metamorphosed rock, intermediate in grade between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky sheen to the surfaces of cleavage (or schistosity)."},{"code":"5.5","name":"Schist","parent":"5","scope":"A strongly foliated crystalline rock, formed by dynamic metamorphism, that can be readily split into thin flakes or slabs due to the well developed parallelism of more than 50% of the minerals present, particularly those of the lamellar or elongate prismatic habit, e.g. mica and hornblende."},{"code":"5.14","name":"Serpentinite","parent":"5","scope":"A rock consisting almost wholly of serpentine-group minerals derived from the hydration of ferromagnesian silicate minerals such as olivine and pyroxene."},{"code":"5.12","name":"Skarn","parent":"5","scope":"A rock of complex mineralogic composition formed by contact metamorphism and metasomatism of carbonate rocks.  It is typically coarse-grained and rich in garnet, iron-rich pyroxene, epidote, wollastonite, and scapolite."}],"rt":[]}