In a large pot, combine the peaches with 475g / 16.76oz of sugar. Combine the remaining sugar with the pectin and set aside.
Cook the peaches over medium-high heat until the flesh is tender and the pits and skin come off easily, about 45 minutes. Pour in the sugar-pectin mix while stirring constantly, then stir in the lemon juice and cook for 5 more minutes, or until the jam has visibly thickened.
Let the jam cool, then pass it through a drum sieve. Reserve refrigerated for up to 1 month.