I believe the grit to be a growing medium.Maybe it accidently on purpose gets stuck to the harvest in some way and at some time during transit.Correct me if you know better.
The only test is to try a smoke.Normally it is quite evident upon the first inhalation.Especially if you happen to be chewing gum as i do quite often.The gum will soon pick the grain from your teeth/mouth.You will know it's there!
Don't buy it is the easy solution.There are some known health hazards of smoking this shit.One of them,maybe lesser than most but nonetheless still not nice is mouth ulcers/blisters!
Tell your man if they want good dollar you want good shit in return!
I have'nt been near it since first establishing it was in circulation.To my knowledge in my area from about early 06 but to my surprise,a friend 10mins away said that's all he's been getting it for the last 2 mths!!