breccia - hydrothermally altered breccia in jasper - hand specimen
A breccia, from the Italian for broken, is a rock composed of angular broken fragments that have later been cemented. When the fracturing is a result of faulting, there may be displacement of the rock fragments or clasts. Clast refers to the fragments, from the Greek, klastos, for broken in pieces.
Initially a mud or silt that desiccated and contracted, this breccia was hydrothermally altered by solutions bearing silica. The hydrothermal fluids filled the fractures, rounded the clast edges and cemented the fine sediment particles, forming a yellow jasper. It was collected near Ojinaga, Chihuahua, Mexico.
The clasts show some displacement, though it's close to a crackle breccia, where the clasts have not been displaced. In this example, it's best described as a breccia that shows hydrothermal rounding of clast edges. Cut on both sides, but not polished. Both sides are shown.
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