Sourcing Clay in Thermal

Sourcing Clay in Thermal was a day-long field trip to West Coast Sand & Gravel in Thermal, California to scope out clay for upcoming adobe projects in the Pioneertown/Joshua Tree area. The mountains you are seeing in the pictures below are made of almost pure clay. The extracted material is hard as a rock and super cohesive when mixed with water. A key step to working with this type of (montmorillonite) clay is to screen it down to at least a 1/4" particle size (even smaller is better) before blending it with water and aggregate. After collecting some field samples we ran the clay through a barrel sieve (imported from Germany) that attaches to the front of a concrete mixer and breaks the clay down to a workable size. Initial soil tests are pointing towards a mix ratio of 1 part clay to 8 parts sand for adobe block and plaster mixes. This type of clay is also perfect for making light straw mixes.