sedimentary
Conglomerate
Conglomerate (clastic sedimentary rock)
Hardness: variable depending on clasts (usually 3-7); Color: brownish-grey matrix with multi-colored rounded pebbles; Luster: dull/earthy; Texture: coarse-grained clastic; Cleavage: none.
- Hardness
- variable depending on clasts (usually 3-7)
- Color
- brownish-grey matrix with multi-colored rounded pebbles
- Luster
- dull/earthy
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Physical properties
Hardness: variable depending on clasts (usually 3-7); Color: brownish-grey matrix with multi-colored rounded pebbles; Luster: dull/earthy; Texture: coarse-grained clastic; Cleavage: none.
Formation & geological history
Formed in high-energy environments like riverbeds, shorelines, or alluvial fans where water currents are strong enough to transport and round large pebbles before they are buried and cemented by finer sediment (silt/calcie/silica). The location in Mindanao (Lanao del Norte area) is consistent with sedimentary deposits near volcanic and river systems.
Uses & applications
Commonly used as a decorative stone, fill material in construction, and as a coarse aggregate in concrete. It is also highly valued by geologists as an indicator of ancient river flow directions.
Geological facts
Conglomerate is often called "puddingstone" because the rounded pebbles look like raisins in a pudding. It is distinguished from breccia by its rounded clasts, which indicate the fragments traveled a long distance.
Field identification & locations
Identify in the field by looking for rounded, pebble-sized rocks embedded within a finer-grained matrix. It is very common in river valleys and coastal regions of the Philippines where tectonic activity and high rainfall drive heavy erosion.
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