I have 2 Top-bar beehives. I placed nuggets at the entrance right away when they were installed in early May. Both colonies have made 6 1/2 combs and are doing well. Yesterday I placed the powder in a dish at each entrance. Today to my astonishment, it was all gone! The bees took the powder into the hives in one day!
Update: June 13, 2019
I removed the plastic dishes and realized the landing board on both hives have been stained black from the shungite powder, which has apparently been tracked. This was the case in the above photo of the empty dish but I didn't notice until I removed the dish. I am curious to see if I can see traces of the powder on the inside of the hives, which I will investigate soon. July 24, 2019 Both my top bar hives are thriving. They filled up when I was out of town and I went in to one this morning to take out combs and give them some more room. I took out 3 big beautifully formed honeycombs! That is by far the most I have ever taken out mid-season. I was awed. The only difference this year is the Shungite, so I am really thinking it has had something to do with how much the hives are thriving. Also, I've never actually had both hives booming at once. I usually have 2 boxes, and ever year one thrives and the other flails. But not this year. They are both booming! All I have done is kept the shungite pebbles at the entrance, and at the beginning of the season I gave them each an ounce or two of shungite powder. I am really pleased with the results so far! And despite the crazy heat we've been having, the bees seem happy, to boot!