You can just sub the blueberries for raspberries.

Or you can use the spiced recipe, and leave out the spices.

If it was me - I would look at the pectin package. Take half the amount of peaches with half the corresponding sugar for the peach recipe. Then I would take half the amount of blueberries and half the corresponding sugar for the blueberry recipe, and use those quantities for a batch of jam.

If you have a recipe that uses raspberries and pectin, I'd just sub the blueberries, adding them in same proportion and at same time as it says for raspberries. Or use the spiced recipe without the spices as pixie lou said.

Madelaine Bulwinkel has a Peach Blueberry Jam but it doesn't call for pectin. If you can't find a recipe you like, I suggest following the peach recipe on the pectin box, but reduce the peaches by the amount of blueberries you plan to add. Cook the peaches and pectin as directed, then I would try adding the blueberries *just* before (maybe 3-5 minutes) you add the sugar. Madelaine adds hers just 5 minutes before taking off the heat to can. HTH

With jams you can mix any fruit combinations you wish as long as the total amounts stay the same. You don't need a specific recipe for whatever fruits you want to use. Only exceptions would be the low-acid fruits like figs, mangoes, and windfall apples.

If the recipe calls for 4 cups fruit you can use 2 cups each, 1 cup of one and 3 cups of the other, etc. Even 3 fruit jams are easy to make. Most of the pectin boxes provide a set of mixed-fruit instructions.

Dave