The use of site sourced soil for earthen construction goes back as far as earthen construction itself. Even today in many developing countries it remains the most viable option. In North America it is still commonly used for adobe and compressed earth block structures. Its use in rammed earth, however, is becoming increasingly rare. We at De la Tierra are not ready to dismiss site soils as a matter of course. If after thoughtful consideration or simply as a matter of preference, the decision is made to source material from off-site, either in total or as a blend with site material, the desired characteristics of the final mix do not change. Soil either is or is not 1) suitable for walling, or 2) amendable to become suitable. Regardless of the source, some level of processing will be required to attain standards suitable for use in modern walls. Different sourcing options will inevitably present different challenges and advantages, so a thorough approach to locating the best source is one of the most important components of your project. For site soils this involves mapping, quantifying, extraction, screening, blending and testing, for starters. For quarried material there will be visits to the pit to collect samples and consultation with the quarry master, review of the quarry specs, testing for conformity and non-specified characteristics, as well as consideration of transportation costs. The value of having experts to help guide this process is hard to overstate.