Cut the skin of the peaches crosswise. Blanch the peaches briefly in boiling water, rinse and peel off the skin. Halve the fruits, stone and cut into small cubes. Mix 950 g pulp with jam sugar, rum and lemon juice in a large pot.
Boil up the fruit mixture while stirring. Let it boil for about 4 minutes while stirring. Possibly make a gelling test. Fill jam brimful into prepared twist-off jars. Close the jars immediately. Let it cool down.