There is no evidence to prove that taking a bath using granite rock will kill coronavirus (COVID-19).
According to the World Health Organization (WHO) and the U.S. Food and Drug Administration, to date, there is no vaccine and no specific antiviral medicine to prevent or treat COVID-19. Possible vaccines and some specific drug treatments are under investigation.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.