Prepare the Oranges: Wash blood oranges, cut six into quarters and thin slices, place in a saucepan, cover with water, boil, then soak for at least 8 hours.

Strain and Juice: Strain orange slices, squeeze juice from remaining six blood oranges and mix with soaking liquid to have 4 cups.

Combine Ingredients: In a Dutch oven, add orange slices and combined juice, add sugar and lemon juice, mix well.

Cook the Marmalade: Bring to boil, reduce heat, and simmer for about 20 minutes until gel stage is reached.

Prepare for Canning: Sterilize jars, ladle in marmalade leaving 1/4 inch headspace.

Process the Jars: Seal jars and process in boiling water bath for 10 minutes (15 minutes above 6,000 feet).

Cool and Check Seals: Let jars cool for 24 hours, check that lids are sealed.