This is an acorn dropped from the the branches of a magnificent Coast Live Oak that grows in my yard. Coast Live Oaks grow in groves in the Santa Monica Mountains.
Acorns from these oaks were a major part of the diet of native Chumash and Tongva people who lived in Southern California, in these mountains and on the Channel Islands. The nuts were shelled and then ground to a powder in stone mortars. The tannin in the meal was flushed out by rinsing in water. Then porridge was prepared by boiling the oak flour with water.The Chumash were expert basketweavers, whose exquisite baskets are displayed in museums today. The baskets were so tightly woven they could hold water. The porridge was cooked by heating red-hot rocks, then plunging them into the porridge-filled baskets.
Edible? I should say so. They are certainly being eaten by all the squirrels that scamper under the oak branches, on the roof of my house!