{"thcode":4,"term":{"code":"5.7.3","name":"Orthogneiss","parent":"5.7","scope":"A gneissic rock formed from an igneous parent"},"uf":[],"bt":[{"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","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."},{"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":[],"rt":[]}