Acasta gneiss - ROM2004_1037_15


Acasta gneiss

Geography: Northwest Territiories, Canada, Northwest Territories, Acasta River
50 × 20 × 25 cm, 40kg
    • Attributes
    • Objects
    • Petrology Taxonomy
    • Metamorphic
    • Specimen CategoryGneiss
Object number: ROMESG37446
Credit Line: Gift of the ROM Reproductions Fund
Not on view
DescriptionThis specimen is a piece of the oldest rock in the Earth’s crust that has been dated: it was found to be 4.03 billion years old! It was collected from a body of rock that occurs about 350 km north of Yellowknife in the Northwest Territories near the Acasta River. Originally a tonalite in composition, it was subjected to a period of high temperatures and pressures which resulted in a layering referred to as a “gneissosity”. Tonalites similar to the Acasta gneiss occur throughout the rock record, which means that some of the familiar mineral and rock-forming processes operating today began very early in Earth’s history.
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