Blueberry Marmalade

I love blueberry pie. I wasn't loving "freezer" blueberry jam, which isn't cooked. It dawned on me recently, why not make a cooked blueberry jam? I found just the thing in Preserving the Taste, by Edon Waycott (out of print, available used or try your library).
Here is my adaptation:

Ingredients

• 1 orange plus juice
• 1 lemon plus juice
• [total juice should equal 1/2 c]
• 1.5 c water

• 4 c  fresh blueberries or 2 12oz bags frozen, thawed, crushed
• 3 c cane sugar
• 1/4 tsp cardamom

Directions

• Cut off ends of orange and lemon, extract juice
• Seed then pulverize all in a food processer, place in good sized pot
• Add water, boil 10 minutes
• Add juice, boil another 15 minutes
• Add blueberries, sugar, spice
• Cook uncovered 20 minutes or until reaches set temperature of 220º
• Fill jars, process to seal or freeze