Quartzite cobble |
|
 QuartziteThis quartzite cobble displays conchoidal fractures on its surface (called percussion marks) that formed from this cobble banging into other rocks along its long journey from the mountains of central Mexico to the shoreline gravel bars in San Diego (a journey that may have taken a billion years to complete!). This is a beach cobble from Carlsbad, California. |
| https://gotbooks.miracosta.edu/rocks/metamorphic/16.html | 2/2/2021 |