Is rip rap always limestone?
Bill, no. "Rip Rap" can be almost anything that is heavy and solid to prevent erosion...even cars. Limestone is often used because it is the most common substrate there is. It is normally cheap, readily available, lasts for decades, and adds some minor benefits benefits in water chemistry and pH buffering. Limestone needs to be pulverized smaller than a 60 mesh to be "fast" acting in pH buffering/change.
