Sierra Nevada Fieldstone Moss Boulders aka Oakdale Boulders Granite and Basalt The foothills of the western side of the Sierra Nevada mountains have vast grassy ranch lands. We and other boulder wranglers harvest the moss covered boulders that can limit use of these lands. The types of rock material that are commonly found are granite, basalt and lava rock. These boulders are usually gray or black in color and covered in full or in patches with lichens and various types of moss. The reddish boulders seen in California landscapes are known are Sonoma Fieldstone, are not part of this group.
