Is fossil shell flour good for you

Sea shells in powder form are the basis for many health supplements, often listed under calcium. They contain calcium and magnesium, good for bones and the nervous system and general health. I used to take dolomite tablets for pre-menstrual discomfort, and they worked for me. (Dolomite is one word for the type of naturally occurring matter.)

I haven't heard of 'flour' form, but it is indeed a white or grayish powder when mined. Usually it is formed into tablets.