So rethinking the ID on some. Engelmann oak is a California native, but rare. Here there seemed to be volunteers all over the place so I was suspicious. The leaves are very similar to southern live oak (Q virginiana), but that's not a Cali oak. Turns out the city of Fresno has been planting southern live oak as street trees for years. I found a street near me that has several, and that's where I was gathering acorns. So, now I'm pretty sure the darkest acorns in the pic above are from southern live oak.