The Rio 2016 silver Olympic medal is pictured at the Casa da Moeda do Brasil (Brazilian Mint) in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRU1
Nelson Carneiro, craftsman from the Casa da Moeda do Brasil (Brazilian Mint) works on the Rio 2016 Olympic medal mold in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRU4
A worker from the Casa da Moeda do Brasil (Brazilian Mint) pours molten metal into a mold to prepare the Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRU5
A worker from the Casa da Moeda do Brasil (Brazilian Mint) prepares Rio 2016 Olympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUG
A worker from the Casa da Moeda do Brasil (Brazilian Mint) prepares Rio 2016 Olympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUJ
A worker from the Casa da Moeda do Brasil (Brazilian Mint) prepares a Rio 2016 Olympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUL
A worker from the Casa da Moeda do Brasil (Brazilian Mint) checks a Rio 2016 Paralympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUU
A machine works on a Rio 2016 Olympic medal at the Casa da Moeda do Brasil (Brazilian Mint) in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUY
The Rio 2016 gold Olympic medal is pictured at the Casa da Moeda do Brasil (Brazilian Mint) in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRU3
A worker from the Casa da Moeda do Brasil (Brazilian Mint) prepare Rio 2016 Olympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUE
A worker from the Casa da Moeda do Brasil (Brazilian Mint) puts plates to prepare the Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRTU
A worker from the Casa da Moeda do Brasil (Brazilian Mint) varnishes a Rio 2016 Olympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUW
The Rio 2016 bronze Olympic medal is pictured at the Casa da Moeda do Brasil (Brazilian Mint) in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRU0
A worker from the Casa da Moeda do Brasil (Brazilian Mint) prepares a Rio 2016 Paralympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUD
A worker from the Casa da Moeda do Brasil (Brazilian Mint) shows a Rio 2016 Olympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUI
A worker from the Casa da Moeda do Brasil (Brazilian Mint) takes out gold-plates Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUS
Workers from the Casa da Moeda do Brasil (Brazilian Mint) prepare the Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRTZ
Nelson Carneiro, craftsman from the Casa da Moeda do Brasil (Brazilian Mint) works on the Rio 2016 Olympic medal mold in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUC
A sculptress from the Casa da Moeda do Brasil (Brazilian Mint) works on the Rio 2016 Olympic medal at her computer in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUA
A worker from the Casa da Moeda do Brasil (Brazilian Mint) takes out gold-plated Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUF
Workers from the Casa da Moeda do Brasil (Brazilian Mint) prepare Rio 2016 Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUH
A worker from the Casa da Moeda do Brasil (Brazilian Mint) cleans a Rio 2016 Olympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUM
A worker from the Casa da Moeda do Brasil (Brazilian Mint) cleans a Rio 2016 Olympic medal in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUP
A worker from the Casa da Moeda do Brasil (Brazilian Mint) takes out gold-plated Rio 2016 Olympic and Paralympic medals in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRUZ
The Rio 2016 Olympic medals are pictured at the Casa da Moeda do Brasil (Brazilian Mint) in Rio de Janeiro, Brazil, June 28, 2016. REUTERS/Sergio Moraes - RTX2IRV1
Making a Rio Olympic medal
The medals that will be awarded at Rio are the most sustainable in Olympic history: much of the silver is recycled from old mirrors and X-ray plates; the gold is free of mercury.
