Emerald

Emerald gems are characterized by their variable-strength slowing poison debuff, below-average range, neon green damage type and low single-target shot combined with stronger poison damage giving them altogether above-average damage. Some emerald gem combinations are only gems in the game with stunning ability.

Once an enemy is poisoned, they can't be poisoned again until the pre-existing poison runs out.

Waves that are weak to Emerald are 5,6,11,22,26 and 30. On survival mode, you can begin with Malachite, which deals neon green damage.