Which one of the following is an example of both an igneous as well as a metamorphic rock ?
Gabbro
Geyserite
Gneissoid
Granite
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UPSC NDA-2 – 2024
– Metamorphic rocks are formed from pre-existing rocks (igneous, sedimentary, or other metamorphic rocks) that are subjected to high heat, pressure, or chemically active fluids, causing changes in their mineralogy, texture, or chemical composition (e.g., Gneiss, Marble, Slate).
– Gneiss is a high-grade metamorphic rock characterized by distinct banding (gneissoid texture) formed by the segregation of different minerals. It can be derived from various parent rocks, including igneous rocks like granite (forming granitic gneiss) or sedimentary rocks like shale.
– Gabbro is an igneous rock. Geyserite is a form of opal or chalcedony deposited by hot springs or geysers (often considered a chemical sedimentary deposit or mineraloid). Granite is an igneous rock.
– Gneissoid specifically describes the texture of Gneiss, a metamorphic rock that frequently originates from igneous precursors like granite, thus representing a link between the two rock types.