Peel the quinces, clean them and cut them into small pieces. Clean and slice the pears without the white part. Peel the mandarins, separate them into pieces and save the rinds of three mandarins. Cut the rinds into very fine pieces. Boil the water in a large pot with the sugar, add the cinnamon and the mandarin rinds.
Allow to boil for 5 minutes, then add the mandarins, pears and quinces. Stir and leave to boil, occasionally stirring. Once the syrup starts to thicken, you need to start stirring constantly.
The jam is ready once the quinces turn red and the syrup thickens. Distribute the hot jam into preheated jars, remove the cinnamon stick. Close them, turn upside down and leave them as is for one night.