S.C. Code Ann. § 10-9-190

Each person to whom a license shall be issued must, at the end of every month, make to the Comptroller General a true and lawful return of the phosphate rock and phosphatic deposits he may have dug or mined during such month and shall punctually pay to the State Treasurer, at the end of every quarter or three months, a royalty of five cents per ton upon each and every ton of the crude rock (not of the rock after it has been steamed or dried), the first quarter to commence to run on the first day of January in each year.