Hi, Jim. Let me add to the questions. 1. sometimes a rubber washer will disintegrate and cause your water to do funny things. Is the black coming from more than one fixture? Sounds like it is mainly from the toilet?
2. Have you noticed any standing water on the streets in your area? Did you ask your neighbors if they are having problems? Are you on city water or a well?
3. Have you or any brothers or sisters been hanging on, swinging on, or otherwise moving any of the pipes around? Is the water pipe in your house CPVC (plastic), copper, or galvanized steel?
4. If they strike oil on your property, will you cut John2000 and I in on the royalties? LOL