Since 2011, Cal ACS has participated in all but one of the annual Bay Area Science Festivals, wrapping up the NCW season with Discovery Days at AT&T Park in San Francisco.  This free event attracts over 30,000 visitors, and features around 200 companies and community organizations.  On Saturday, November 11th, visitors were fascinated by Professor Peter Olds' mineral samples, and most took Periodic Tables and copies of the NCW 2017 edition of Celebrating Chemistry, "Chemistry Rocks!"  Kids tried out the crystal-growing activities, and took colorful borax solutions with them to watch the progress later.  We were ably assisted by enthusiastic volunteers from the Alpha Chi Sigma chemistry fraternity at UC Berkeley.