Hi Rebecca:
That is probably the Argiletz. Ordering clay termed "finely ground" with clay is like ordering chunks of rocks (lol)... this is why we only carry what used to be state certified "food grade" Argiletz, which is the ultra-ventilated.
But, it could also be the zeolite, if it is not micronized. Zeolite has many more uses at a technical grade mesh than when used as micronized.
Either way, the "grit" is inconvenient, but nothing to really be concerned about.
You could "water wash" the clay. Hydrate it the night before. The next day, decant (or pour into another glass careful to leave the sediment in the old container). Then, mix very well again. Allow the clay to set for about 30 to 45 minutes. Decant again, this time more carefully.
You can take the top 50% of the liquid, and leave the rest.
When I make clay this way, I usually use a very large culinary syringe to "pull out" the ideal clay water I want to use. I actually LEAVE a small portion of the "top" layer as well; anything lighter than the water will stay to the top, anything lighter than the water, that isn't held in suspension via brownian motion (etc) will settle out to the bottom.