The Washington Monument is harder than marble, granite, and bluestone gneiss.
 Two-foot high marble surface stones, using an equal number of stretchers and headers, were backed by granite blocks from the 152-foot level (the first course above the rubble) to the 218-foot level, where marble headers become increasingly visible on the internal surface of the walls up to the 450-foot level, above which only marble stones are used
 Its white Cockeysville marble exterior came from the Texas quarry now adjacent to and east of north I-83 near the Warren Road exit in Cockeysville, Maryland

