There are two kinds Luster dust the which is shiny and awesome for wedding cakes (which now come in spray cans) and petal dust.
They are used for gumpaste and fondant flowers.It make the colors more vibrant and life like.I usually use the pedal dust and then luster (pearl) to make them look nice.I actually just used the gold luster dust( all edible) for some bamboo on a wedding cake 
Hope that helped.BTW they usually run about $3.50 each .They also have edible glitter called pixie dust and disco ball
I think I own what you're talking about. The colors are coarser than petal, luster dusts, etc.
The brand I find most commonly are from CK. I bought most on line, the link will get deleted. I have found them at my local cake supply store.
I bought them for dark colored buttercream icing, but now I use them to color white chocolate.
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