sedimentary
Conglomerate
Conglomerate (Rock composed predominantly of rounded clasts > 2mm)
Hardness: Variable (typically 6-7 depending on cement and clasts); Color: Variable greys, tans, and browns; Luster: Dull/Earthy; Crystal Structure: Clastic (rounded fragments embedded in a finer matrix); Specific Gravity: 2.1-2.6
- Hardness
- Variable (typically 6-7 depending on cement and clasts)
- Color
- Variable greys, tans, and browns
- Luster
- Dull/Earthy
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Physical properties
Hardness: Variable (typically 6-7 depending on cement and clasts); Color: Variable greys, tans, and browns; Luster: Dull/Earthy; Crystal Structure: Clastic (rounded fragments embedded in a finer matrix); Specific Gravity: 2.1-2.6
Formation & geological history
Formed in high-energy environments such as riverbeds, alluvial fans, or beaches where water is strong enough to transport and round large stones. Over millions of years, these sediments are buried and lithified by mineral cements like calcite or silica.
Uses & applications
Used primarily in the construction industry as coarse aggregate for concrete and road base. Occasionally used as a decorative building stone or for ornamental landscaping.
Geological facts
Conglomerate is often called 'puddingstone' because the rounded stones look like raisins or nuts in a pudding. It is one of the most common rocks found on Mars by rovers, proving the past existence of ancient flowing rivers on the red planet.
Field identification & locations
Identify by looking for rounded pebbles or cobbles (not sharp angles) 'glued' together in a matrix. Commonly found along ancient or modern river channels and shorelines. Look for it in areas with exposed sedimentary layers.
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