In the course of teaching my Soil Mechanics class, I’ve tried numerous different charts and methods for teaching the Unified system of soil classification. Probably the most success I’ve had is with the one from NAVFAC DM 7, and it’s below. (I’ve included the plasticity chart for completeness.)
An example of how this works is here.
NAVFAC DM 7 remains a popular reference book for geotechnical engineers, and ordering information is here.
vulcanhammer.net 
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