I made a brief reconnaissance of the land just north of Mountain View Cemetery last week and captured a few more knockers. Poison oak is abundant here, I should report. It’s a lovely thing to see pristine outcrops, although the geologist in me wished for a handy rock hammer. In its absence, I can only say that this and the next knocker looked like typical sandstone or greenstone from the Franciscan mélange making up the area.
This next knocker is definitely chert of the high-grade type found elsewhere in Upper Rockridge. Notice that it supports less vegetation, being poorer in nutrients.
My reconnaissance was brief because the area is undergoing development, and while I didn’t notice a no-trespassing sign where I passed the fence I felt the need for discretion. The best knocker of the area, unfortunately, is under attack (click full size):
The upper body of red chert is still living bedrock while the nearer pile is loose pieces of it. I don’t know what is being planned for the area, but the chert would look nice in a fairway, or left in shabby gentility like some of its siblings.
Oakland Geology 
19 September 2008 at 9:01 am
I picked up some chips, myself. My personal policy in Oakland is to treat the whole city, except for roadcuts, like parkland. I should probably write a new entry to explain why. For now, let me note that I do not encourage hammering anything, on private or public property, without securing permission first.
18 September 2008 at 11:32 pm
cool. never thought to walk up there, i’ve been so conditioned to avoid construction zones. guess they wouldnt mind if you hammered some samples given that they are totally destroying these knockers anyway.