1. a metamorphic rock with a banded or layered structure formed by the alteration of granite or other rocks under heat and pressure
Usage: geology

Examples

• The mountain was composed primarily of gneiss with distinctive light and dark bands.
• Geologists identified the ancient gneiss formation as being over two billion years old.
• The hiking trail passed over exposed gneiss bedrock.
• Gneiss is commonly found in the cores of mountain ranges.
• The distinctive striped appearance of gneiss makes it easy to identify in the field.
• Construction workers quarried gneiss for use as building stone.