leaching. Phosphate leached from guano phosphatizes the underlying rocks in some areas, forming apatite where the host rock is limestone and forming aluminum- or aluminum-iron-phosphate minerals where the underlying rock is a silicate. Individual deposits of both igneous apatite and marine phosÂ­
Medicare Part B (Medical Insurance) covers diagnostic hearing and balance exams if your doctor or other health care provider orders these tests to see if you need medical treatment. Medicare doesn't cover routine hearing exams, hearing aids, or exams for fitting hearing aids.
Medicare Part A is funded by the payroll tax (FICA) that is deposited into the Hospital Insurance Trust Fund. Most people who have a personal or spousal work history and paid into Social Security do not have to pay a premium for Part A.