Gneiss

Metamorphic rock that forms under intense pressure and high temperature and that is made of quartz, feldspar, amphibole and mica. Gneiss represents the highest grade of metamorphic rock, which is characterized by alternating bands of dark and light-colored minerals, foliation (i.e., parallel alignment of planar minerals) and tight folding. This rock type is common at mid to deep levels of continental crust.

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Word of the Week – Drill Core

Word of the Week – Drill Core

Drill Core Intact cylindrical shaped sample of rock obtained during drilling with a special coring bit. Although commonly narrow in diameter (e.g., 1-4" or 25-100 mm), it preserves a...

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Word of the Week – Drill Cuttings

Word of the Week – Drill Cuttings

Drill Cuttings Small chips of rocks (e.g., <1/8 inch or <3 mm) obtained during drilling with a rotary bit that are continuously returned to the surface by the circulation of mud....

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