Metaconglomerates form by metamorphism of conglomerate. The general shapes of the original gravel are usually well preserved. Metaconglomerates have a clastic texture and are composed of rounded to subrounded gravel surrounded by finer-grained matrix. Sometimes, strongly directed metamorphism results in a stretched-pebble conglomerate, which has elongated gravel clasts.
Metaconglomerate (“Black Marinace Gold Granite”; sometimes considered “Black Mosaic Granite”; also apparently (?) known as “Black Morgan Granite”) - this attractive Precambrian-aged polymict metaconglomerate from Brazil has small-scale interpenetrating pressure-solution contacts between clasts in many areas (see lower right, upper central-left, upper central-right).
Metaconglomerate (“Marinace Green Granite”) - this Precambrian-aged polymict metaconglomerate from Brazil has clasts are dominated by igneous & metamorphic rocks. The greenish matrix is epidote-rich.
Metaconglomerate (“Marinace Red Granite”) - another Precambrian-aged polymict metaconglomerate from Brazil. This rock has a nice dark reddish-colored matrix and clasts of variable size and composition (mostly igneous & metamorphic, plus relatively common epidotized clasts). Other commercial names that appear to have been applied to the same rock include “Paladium Granite”, “Palladio Granite”, and “Palladio Vesuvio Granite”.