Open windows or set up portable fans to supply more ventilation in the room and put on rubber gloves.
Clean the chip in the marble sink before repairing it. Wipe the chipped marble sink and detached marble fragment with a cloth dampened in acetone.
Dampen another cloth with water. Wipe the chipped marble sink and detached marble fragment to rinse off the acetone.
Dry the chipped marble and detached marble fragment with a towel.
Squeeze equal proportions of the components in a two-part epoxy glue kit onto a mixing board or coffee can lid. Stir the components together using a wooden craft stick.
Brush the epoxy into the chipped portion of the marble sink and onto the detached marble fragment using a paintbrush. Press the marble fragment into the chipped marble.
Wipe any glue oozing out of the patch with another acetone-dampened cloth.
Cover the repaired marble with a heavy object.
Let the glued marble cure for 24 hours.