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Plutonic Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Ultramafic rocks, because they are mostly made of mafic minerals, are commonly dark colored (if unaltered), but some peridotites are light green because they contain abundant olivine. The peridotite in Figure 6.29 contains large conspicuous green clinopyroxene crystals surrounded by finer-grained olivine weathered to a light brown color. Figure 6.13i shows a peridotite that contains garnet. Because ultramafic rocks are quite unstable at Earth’s surface and at shallow depths in Earth, they often alter to produce green serpentinites that are mostly made of serpentine, chlorite, and iron oxides (Fig. 6.10).
Minerals, rocks, discontinuities and rock mass
Published in Ömer Aydan, Rock Mechanics and Rock Engineering, 2019
Serpentinite is comprised of serpentine minerals. Minerals in this group are formed by a hydration and metamorphic transformation of ultramafic rocks. Serpentinite is formed from olivine via several reactions. It can be easily weathered, resulting in swelling.
Integrated feed management of mineral processing plants with application to chromite processing
Published in Canadian Metallurgical Quarterly, 2021
F. A. Peña-Graf, T. Grammatikopoulos, A. Kabemba, A. Navarra
Mineable chromium occurs mainly as natural chromite, which is a chromium spinel that varies in composition according to the chemical formula (Fe,Mg)O⋅(Cr,Al,Fe)2O3. The majority of the World's commercially viable chromite is mined from mafic and ultramafic rocks. These ores can be subdivided into stratiform and podiform. Stratiform ores are associated with mafic/ultramafic layered intrusions, are Precambrian in age, and have an intracratonic setting. Podiform ores are mainly Phanerozoic in age, have a highly irregular geometry, and are associated with ophiolites [10]. Major associated gangue minerals are Fe-Mg silicates and their alteration products, such as talc, serpentine, amphibole, chlorites, and Fe-(Ti)-oxides.