ROCK MULCH

Rocks can be used as mulch in the landscape. Use river rock or pea gravel to maintain a proper size and color in the landscape.
Avoid using ground limestone or marble. The cost of the former may be ideal, though limestone (calcium carbonate) will alter the soil pH, resulting in yellowing of evergreens and other plants.Marble is a metamorphic form of limestone, which means it still is calcium carbonate and will raise the pH, though much slower.