sedimentary
Conglomerate (Red Sandstone variety)
Clastic Sedimentary Rock (Conglomeratic Sandstone)
Hardness: 6-7 (based on quartz content); Color: Reddish-brown due to iron oxide (hematite); Luster: Dull or earthy; Crystal structure: Non-crystalline clastic texture with rounded pebbles; Cleavage: None; Specific gravity: 2.6-2.8
- Hardness
- 6-7 (based on quartz content)
- Color
- Reddish-brown due to iron oxide (hematite)
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 (based on quartz content); Color: Reddish-brown due to iron oxide (hematite); Luster: Dull or earthy; Crystal structure: Non-crystalline clastic texture with rounded pebbles; Cleavage: None; Specific gravity: 2.6-2.8
Formation & geological history
Formed through the lithification of rounded river or beach gravel and sand. The red coloration indicates formation in an oxygen-rich terrestrial environment, such as ancient riverbeds or alluvial fans, often dating back to the Triassic or Permian periods.
Uses & applications
Primarily used as a construction aggregate, road base material, or decorative stone in landscaping and architecture. Some high-quality specimens are used by collectors to demonstrate sedimentary processes.
Geological facts
Conglomerates are often called 'pudding stones' because the pebbles looks like raisins or nuts in a cake. They are important indicators to geologists of high-energy water environments like fast-moving rivers.
Field identification & locations
Identify in the field by looking for rounded, water-worn pebbles cemented within a finer-grained sandy matrix. Common in the Southwestern United States, parts of the UK, and ancient mountain belts. Look for individual grains that appear 'glued' together.
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