Gneiss/ Migmatite (ID:052) GEOLOGICAL CLASSIFICATION (Genetic classification) Introductory Gneiss: This rock is a gneiss of banded colours. The lightest-colored part of rock definition (visu) corresponds to quartz and feldspars whereas whereas the darker part contains to biotite.
Mig: This rock is a migmatite of banded colours. The lightest-colored part of migmatite corresponds to quartz and feldspars whereas the darker part contains to biotite. Petrologist's Gneiss: This rock is a gneiss. This banded rock present lightest-colored quartz and definition feldspars with fine to medium crystal size (0.5-1mm) whereas whereas the darker part contains to biotite of fine size.
Mig: This rock is a migmatite, which is a mixture of metamorphic rock and igneous rock. It is created when a metamorphic rock that partially melts, and then that melt recrystallizes into an igneous rock, creating a mixture of the unmelted metamorphic part with the recrystallized igneous part. The lightest-colored part of migmatite (quartz and feldspars) was partially melted whereas the darker part (biotites) remnants of the more or less unmodified parent rock. Quartz and feldspars presents a fine to medium crystal size (0.5-1mm) and bioites have a fine size. Commercial In the Natural Stone Industry, this rock is known as Black Swell. definition (if any) GEOMECHANICAL CLASSIFICATION (Behavioural classification, Goodman, 1989) II. Clastic texture A. Stably cemented. DESCRIPTION OF LOCAL SAMPLE Geological Not available description of local sample Other information Not available about the outcrop Weathering grade of Not available sampling outcrop (ISRM, 1981) Location Not available ENGINEERING CLASSIFICATION OF INTACT ROCKS (General classification) ISRM classification R0 R1 R2 R3 R4 R5 R6 by strength. USC Extremely Very Weak Medium Strong Very Extremely (MPa) (ISRM, 1981) weak weak (5-25) strong (50-100) strong strong (0.25-1) (1-5) (25-50) (100- (>250) 250) Deere and Miller classification by strength and deformation properties (Deere and Miller, 1966)
Mechanical General values Particular (local) properties values (if any) (unaltered) Young’s Modulus (E) Tangent modulus 25-60, Gneiss at 50% ultimate strength (GPa) (Ramirez Oyanguren and Alejano, 2004, p65) Poisson’s coefficient (ν) 0,09-0,2, Gneiss (Ramirez Oyanguren and Alejano, 2004, p65) Uniaxial compressive strength (MPa) 80-250, Gneiss (Ramirez Oyanguren and Alejano, 2004, p65) P wave velocity (m/s) 3000-6000, Gneiss (Orica) mi (Hoek and Brown criterion, 1980) 30 (Migmatite); 33 (Granite) (Ramirez Oyanguren and Alejano, 2004, p65) Basic friction angle (Φb) 26–35, Gneiss (Patton,1966) Physical properties Dry unit weight (kN/m3) 26-27,8, Gneiss 26.35 (unaltered) (Ramirez Oyanguren and Alejano, 2004, p65) Porosity (%) 1–5, Gneiss (Ramirez 1.00 Oyanguren and Alejano, 2004, p65) Engineering uses and It is an excellent building material, which is currently commercialised. others Refences: • Brotons, V., Tomás, R., Ivorra, S. Grediaga, A. Martínez-Martínez, J., Benavente, D., Gómez-Heras, M. (2016): Improved correlation between the static and dynamic elastic modulus of different types of rocks. Mater Struct (2016) 49: 3021. https://doi.org/10.1617/s11527-015-0702-7 • Fourmaintraux, D., 1976. Characterization of rocks; laboratory tests, ChapterIV in La Mécanique des roches appliquée aux ouvrages du génie civil by Marc panet et al. École Nationale des Ponts et Chausées, Paris • González de Vallejo, L.I., Ferrer, M., Ortuño, L., Oteo, C., 2002. Ingeniería Geológica. Prentice Hall. Madrid • Goodman, R.E., 1989. Introduction to Rock Mechanics, 2nd edition. John Wiley and Sons. New York • Hoek, 2006. Practical rock engineering. Available in https://www.rocscience.com/learning/hoeks-corner • ISRM (1981) Rock characterization. In: Brown ET (ed) Testing and monitoring— ISRM suggested methods. Pergamon press, Oxford, p 211 • Ramírez Oyanguren, P. et al. (1991). Mecánica de Rocas aplicada a la minería metálica subterránea. ITGE, Madrid, España • Ramírez Oyanguren, P., & Alejano Monge, L. R. (2004). Mecánica de rocas: Fundamentos e ingeniería de taludes (No. 727). Red DESIR.
Last update: 13/02/2019