The story of blue rock
https://oaklandgeology.com/2026/02/02/the-story-of-blue-rock/
On the rock used for paving early #Oakland (CA) streets.
The story of blue rock

There was a long period in Oakland’s history when the city cared deeply about its streets and took great pains with the rock it used in them. The tiny village that became Oakland in 1852 was …

Oakland Geology