Is Mighty Indigo safe on marble and granite? You bet! Mighty Indigo is only slightly alkaline with a Ph of 10.5 and a patented surfactant that keeps the product from etching natural stone surfaces. Did this answer your question?Yes NoAdditional Comments:Send Feedback Post navigationPrevious post: Can GroutOnce! be used with all grouts?Next post: Can Efflorescence Remover be used on all surfaces? Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Email * Website Save my name, email, and website in this browser for the next time I comment.