Metaconglomerate
Metaconglomerate is a metamorphic rock formed from conglomerate after it is squeezed and heated. Conglomerate is a rock that has pebbles or larger fragments set in a matrix of sand, silt, or clay. In metaconglomerate, the rock may look similar to conglomerate, but the clasts can be deformed by pressure.
In ordinary conglomerate, the cement between the grains is weaker than the grains, so the rock breaks around the grains. In metaconglomerate, the cement has recrystallized and can be as durable as the clasts, so the rock can break through the grains.
When metamorphism produces a foliated texture similar to slate or phyllite, starting from conglomerate rather than clay, you get foliated metaconglomerate.
The metaconglomerates of Jack Hills in Western Australia are famous as the source rocks for many ancient detrital zircons, some dated as old as about 4.4 billion years.
This page was last edited on 2 February 2026, at 02:57 (CET).