When I was in the process of chosing a land for my art studio, the availability of natural building materials on or near the site was an important consideration in the purchase. As the photo shows (starting at the top-left clockwise); the land I selected, has many small rocks on the surface that I use for a variety of purposes: Gravel fill, drainage channels, aggregate for concrete, pathways, etc. Testing the soil revealed ample clay - ideal for making adobe, cob and earthen plasters. The piled stones in the second picture were culled from mountain washes on nearby federal land; and used for the construction of stem-wall footings. A heavy metal screen for sifting clay and river sand was purchased from a local metal dealer, who obtained the heavy steel mats from an old mining operation in the area. The last photo shows a dry wash on my property where sand for application in cement mixes, lime plasters and other building uses is obtained. Flash-flooding that occurs each rainy season, replenishes the sand, creating naturally occuring sustainable resource.
The use of local resourses for natural building materials not only saves money, but reduces planet energy consumption associated with the use of excavation/loading equipment, rock crushers, and trucking materials long distances to the project site.