Place the brown sugar in a medium bowl. In a small sauté pan, set over medium-low heat, add the coconut oil and warm until just melted. Turn off the heat and mix in the tangerine oil and peppermint extract (if using). Pour the oil onto the brown sugar and mix using a fork or spoon until thoroughly combined. Divide the scrub between the jars and cover with airtight lid. Mixture will last up to 6 months.
To apply the scrub, take about a scant teaspoon and rub it on your lips for about 1 minute, using your index finger. Take a warm, damp cloth and wipe the scrub away, leaving smooth, refreshed lips.