In your submission, you describe the product at issue as 99.99% pure “Aluminum Oxide Granules” AHP 300G, calcined, alpha-phase, CAS # 1344-28-01. The provided product details indicate that the “Aluminum Oxide Granules” are insoluble in water, white in color, and 1-4 mm in particle size. You state that this product is intended to be used as a raw material in the production of synthetic sapphire.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N312349