Where do you find a clay sample with 90+ percent clay content?
Hint: We didn't find our clay in Claysville although that might be a logical place to begin.
Natural soils can occur as every conceivable mix of sand, silt, clay, and gravel. Classifying them in the USCS or determining their texture in the USDA classification is easier if you're familiar with the end member, or baseline, classification.
Midwest GeoSciences Group has built different soil kits for different purposes over the past 10 years. While building soil kits, we've learned that:
- Finding a source for a certain soil type is excruciating, time consuming and expensive.
- Finding a source that yields consistent soil testing results is extremely rare.
- Manipulating soil mixtures to create a soil type is not pragmatic or efficient.
- Source volumes are limited.
Answer: It took years.
The new USCS CALIBRATED BASELINE SOIL KIT is the result of 10+ years of searching and testing, searching and testing, and searching and testing.
The soil sources are scattered across the Midwestern United States for this kit. One source is 30 feet deep and 900 miles away from the MidwestGeo HQ. Access to fast-moving construction projects that allow sample collection at 30 feet deep require special attention to both timing and safety.
One interesting observation we've made over the past 10 years is the fine-grained variability of The Loess Hills located in western Iowa. Despite our early expectations for uniformity of the wind-blown sediments that comprise The Loess Hills, the fine-grained sediments can be highly variable on the scale of one to two feet. While the fine-grained fraction is mostly Silt, the clay occurs as an unpredictable portion - largely because it's variable depositional scale as a dune. Unlike most dunes that primarily consist of sand, The Loess Hills are also dunes, mostly void of sand. We've photographed the precise undisturbed locations of samples and tested them in a lab to literally map the small scale variation of grain-size. Unfortunately, the grain-size variability of The Loess Hills prohibit predictable and reproducable grain-size analysis and Index Testing and not a good candidate for naturally-occurring soil samples for a soil kit.
Thankfully, we are persistent and MidwestGeo has had a lot of help over the past 10 years to find soil sources that successfully provide predictable and reproducible results. We're grateful for that help, cooperation, and effort to assemble soil batches that help people with practicing and mastering their soil classification skills.
The three fine-grained samples have negligible coarse-grained fractions and are uniquely exquisite for teaching the principles of soil classification for FAT CLAY (CH), LEAN CLAY (CL), AND SILT (ML).
The two coarse-grained samples are designed to teach how to differentiate WELL GRADED SAND (SW) from POORLY GRADED SAND (SP) in the field.
Geo-Professionals benefit from our effort and persistence. The soil kits allow to easily practice and quick familiarity of end member, or baseline, classifications. Anyone can calibrate their skills and ability. You can teach your staff. You can test yourself.
You can also use these calibrated samples in the field to compare to which end member classification most closely resembles the natural soil. The USCS CALIBRATED BASELINE SOIL KIT provides these important end member samples.
Check out this unique and exquisite soil kit here.