Cleaning the Ears
Ear mites are the most common cause of gritty, dark wax in a cat's ears; consult your vet for treatment.
An excess of normal but oily and irritating ear wax is common, particularly in indoor cats. Use a recommended wax remover, then remove the excess wax with a soft cotton ball.
Never poke a cotton swab into the ears: it pushes the wax into the ear canal.