Add Epsom salt to a small bowl and add 1/2 teaspoon of mica powder and stir until mixed well. Set aside 1 teaspoon of the colored Epsom salt.

Combine baking soda, remaining Epsom salt, citric acid, and cornstarch in a medium bowl. Add in essential oils and coconut oil. Slowly add in water and mix until consistency is similar to wet sand and the mixture starts to stick together.

Add a small amount of the reserved colored Epsom salt to the bottom of a bath bomb.

Pack each half of the bath bombs with mixture, slightly over-filling. Firmly press halves together. Set mold aside for at least 15 minutes, and up to 2 hours.

When ready to remove the bath bombs, gently tap the sides of the mold with a spoon, then remove mold.

Allow bath bombs to set for 24 hours before using. Bath bombs can be stored in a container, away from water, for up to 6 months.