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During the early mining boom days at the Black Diamond coal mines in Diablo Mountain the main boom town was Clayton. There is a CEMEX in Clayton now.  I wonder if that is the cement word drop.

http://cemexclaytonquarry.com/

https://claytonhistory.org/history/coal-mining/

It sure is close to Brentwood.  Them Hollywood types sure love to live in Brentwood