The following can damage basalt countertops:

1. Scratches: Basalt is a hard and durable material but it can still be scratched if sharp objects are used on it.

2. Heat: Basalt is a natural stone, so it can withstand high temperatures, but extreme heat can cause damage such as cracking and discoloration.

3. Acid: Acids such as lemon juice, vinegar, and household cleaners can etch and damage the surface of basalt countertops.

4. Moisture: Basalt is a porous material, so it can absorb moisture and become stained or discolored if liquids are left on it for too long.

5. Heavy impacts: Dropping heavy objects or hitting the countertop with a heavy object can cause damage such as cracks or chipping.