The original source of all sand is:
beaches
oceans
rocks
rivers

The original source of all sand is rocks. 

There are various types of rocks and some rocks are broken down into pieces which leads to become sand.  Moreover, sedimentary rocks are formed by the layers of deposition that takes place. The main difference between a sedimentary rock and sediment is that in case of sedimentary rocks the sediments are stuck together to form a hard rock like structure and sediments are normally loose in nature. 

African americans at the time just came out of slavery and needed money to provide for there families. so they joined for the money mainly.