Preheat oven to 400 degrees F. Light grease a 9-inch cast iron skillet (or baking pan of comparable size.)
In a large bowl toss together the berries, sugar, tapioca and lime juice. Set aside.
In another large bowl- stir together the flour, baking powder and salt. Use your hands to blend the coconut oil into the flour mixture, spreading the clumps until the pieces are about pea-sized.
Add the lime zest and then the milk gradually, folding it into the dough. Don't over mix!
Turn the dough onto a lightly-floured surface and use a biscuit cutter to stamp biscuits out of the dough. Arrange the biscuits over the berries. Brush the tops with a little bit of milk and sprinkle with sugar.
Bake for 25 minutes or until the berries are burst and bubbly, and the biscuits are golden.
*I decided to make these biscuits with coconut oil, but regular old butter works well too. If you use butter, keep it cold and cut it into small pieces before working it into the dough.