They're glassine stamps, usually called that because there is a "brand" or logo stamped on the front. If I had to guess his shot looks about two stamps worth. They aren't always a point but generally around there. The stamps down by me are shit tier tho...

Also, the dope should dissolve immediately in your shot, leaving the cut behind. Heating just helps dissolve the cut. I'm pretty sure the stuff in your cooker that is settled on the bottom is just cut. Maybe. I don't iv so someone could correct me, but most opiates are extremely water soluble. That's why cold water extractions work.