Metaconglomerate
Metaconglomerate is a metamorphosed conglomerate with rounded pebbles or cobbles in a recrystallized matrix. Pebbles may appear stretched, flattened, or locked into a hard metamorphic rock.
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Metaconglomerate properties at a glance
| Type | Metamorphic Rocks |
|---|---|
| Chemical formula | Metamorphosed pebble-rich sedimentary rock |
| Mohs hardness | 6.5 |
| Luster | dull |
| Streak | Variable by pebbles and matrix |
| Cleavage | Variable; may show foliation in matrix |
| Fracture | Granular to uneven |
| Specific gravity | 2.65 |
| Transparency | opaque |
| Common colors | Gray, White, Tan, Red, Brown, Black |
| Rarity | uncommon |
Geology & background
Forms when conglomerate is metamorphosed, recrystallizing the matrix and sometimes stretching or flattening pebbles.
Metaconglomerate helps geologists connect original sedimentary environments with later mountain-building metamorphism.
How to identify Metaconglomerate
- Look for rounded pebbles or cobbles inside a hard recrystallized matrix.
- Flattened, stretched, or lens-shaped pebbles support metamorphic deformation.
- Metaconglomerate is usually harder and more recrystallized than ordinary conglomerate.
- Photograph both the whole specimen and close-up pebble-matrix contacts.
Where Metaconglomerate is found
Reported from multiple metamorphic terrains worldwide; verify locality against specimen provenance when available.
How much is Metaconglomerate worth?
| Entry-level specimen | $1 |
|---|---|
| Typical collector specimen | $10 |
| Premium specimen | $75+ |
Metaconglomerate is usually valued for teaching, field context, locality, texture, mineral content, or unusually attractive specimens rather than high gem value.
Common uses
- Field identification
- Metamorphic history study
- Education
- Decorative stone when attractive
Interesting facts
- Metaconglomerate can preserve original river or beach pebbles after metamorphism.
- Deformation may stretch pebbles into lens-like shapes.
- Quartz-pebble metaconglomerates can be very hard and resistant.
Care & safety
Metaconglomerate can vary in toughness, cleavage, and weathering depending on mineral mix and fabric.
Avoid inhaling dust. Do not cut, grind, or polish unknown metamorphic rocks without eye protection and a properly rated respirator.
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