The Gem Theatre was on Corunna Road, next to the "Jade Shoppe" building.Here is some info about the Gem from "Cinema Treasures":http://cinematreasures.org/theater/10018
Thanks for commenting. You might enjoy my book about Flint called "Teardown: Memoir of a Vanishing City," a Michigan Notable Book for 2014 and a finalist for the 33rd Annual Northern California Book Award for Creative NonFiction. Filmmaker Michael Moore described Teardown as "a brilliant chronicle of the Mad Maxization of a once-great American city." More information about Teardown is available at www.teardownbook.com.