igneous
Dacite / Andesite Tuff
Intermediate Volcanic / Pyroclastic Rock
AI-generated identification · may be incorrectHardness 5.5-6.5; light grey to pale greenish interior with dark weathering rind; fine-grained to pyroclastic texture with visible dark phenocrysts.
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Physical properties
Hardness 5.5-6.5; light grey to pale greenish interior with dark weathering rind; fine-grained to pyroclastic texture with visible dark phenocrysts.
Formation & geological history
Formed via explosive volcanic eruptions or cooling of intermediate silica magma in volcanic arc settings such as the Indonesian archipelago.
Uses & applications
Commonly used in local construction aggregate, road base, and as a lightweight building material.
Geological facts
Indonesia contains some of the highest concentrations of intermediate volcanic rocks in the world due to active subduction zones.
Field identification & locations
Identified by a distinct dark weathered crust contrasting against a pale, fine-grained volcanic matrix; commonly exposed in volcanic terrains and riverbeds.
