This rock was found it Easton, Pennsylvania by the Delaware River. I'm just starting to become interested and collecting and hoping to use this site to gain knowledge on the rocks and minerals I find! Thank you!
Your rock looks like quartzite, metamorphic rock derived from a rock that was previously a sedimentary sandstone with gravel to cobble size pieces of quartz.
There is quite abit of metamorphic rocks around Easton, PA. Reference: Geology map of Easton, PA.