It's a classic symbol of communism frequently worn by a Jesuit priest Francis paid respects to.
Around two million people packed into Christ the Redeemer Square in Santa Cruz and beyond to hear the pope's open-air address.
His central message: helping the poor and not judging people by what they can produce.
He said consumerism includes a logic in which everything becomes an object that can be consumed and negotiated. He says that excludes people, but the contrary is necessary for a fulfilling life.
Francis said: “A memorable life needs [the participation] of others."
The pope's main event of the day was a keynote speech to a summit of grass-roots groups.
Francis leaves on Friday for Paraguay, the last stop on what has been called his homecoming tour.