My brother stained my mom's quartz/granite kitchen countertop! Please help!?

I am so sorry, but you have damaged the surface. Caesarstone is heat resistant up to 300 degrees farenheit. If you place a hot pot on the counter, and leave it there, it will damage it. Caesarstone is not treated with a sealant, it does not need to be. furthermore, dont make it worse! As with any surface, CaesarStone can be permanently damaged by exposure to strong chemicals and solvents that undermine its physical properties. Do not use products that contain trichlorethane or methylene chloride, such as paint removers or strippers. Avoid any highly aggressive cleaning agents like oven/grill cleaner that have high alkaline/PH levels.