I just attended my Uncles Jesse F. Ivins funeral today. He was 89. He spent a lot of time in the pines and has written about it but mostly in hard copy. I was searching the net tonight because I remember when I was about 10 my Uncle Jess took my brother for a ride in the woods to see the old clay works. I don’t recall the exact route as you don’t usually notice these things when you are a kid. We left from Chatsworth as my dad and uncle were both members of the Glendora Buck Club. I take it the Buzby you refer to is the one and the same that owned the store.

Anyway we explored a site much like you described. There was one added item. There were large tunnels that I believe my uncle said were for cooling the clay. I remember maybe six of these. They were large enough to walk in but were very overgrown and no way did we venture in. I seem to recall we walked down a dirt ramp into a pit and the tunnels were dug into the sides going off in different directions.

Maybe this is the same place?