metamorphic
Shatter Cone (Impactite)
Shock-metamorphosed rock
Hardness: Variable based on host rock (6-7 typically); Color: Grey, green, brown, or tan; Luster: Dull to earthy; Structure: Distinctive conical or fan-shaped striations (horsetail pattern) radiating from an apex.
- Hardness
- Variable based on host rock (6-7 typically)
- Color
- Grey, green, brown, or tan
- Luster
- Dull to earthy
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Physical properties
Hardness: Variable based on host rock (6-7 typically); Color: Grey, green, brown, or tan; Luster: Dull to earthy; Structure: Distinctive conical or fan-shaped striations (horsetail pattern) radiating from an apex.
Formation & geological history
Formed under extreme pressure (2-30 GPa) during hypervelocity meteorite impact events. The shock wave causes mechanical deformation of the bedrock, creating these unique patterns. Geological age varies by impact site.
Uses & applications
Scientific research, geological education, and collector specimens. Highly valued for proving the existence of ancient meteorite impact structures.
Geological facts
Shatter cones are the only macroscopic evidence of meteorite impacts that can be found in the field without laboratory analysis. They only form in the shock-affected basement rock beneath a crater.
Field identification & locations
Identify by looking for the 'horsetail' radiating striations on conical surfaces. In the field, the points (apices) of the cones generally point toward the center of the impact. Found at sites like Sudbury (Canada), Vredefort (South Africa), and Ries Crater (Germany).
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