Abalone shells are often used for smudging ceremonies by the Native Americans in the United States and Canada.
These abalone shells have been cleaned, bleached, and treated in muriatic acid and/or dipped in a light coating of resin. The outside of the shell is clean, but still rough. They are not recommended for use in food consumption.
When exported from the USA, Mexican abalone shells are subject to USFWS export processing fees at overseas rates, not at NAFTA rates as one would think.