Back in the 60's it was common for LSD to be sold as pressed pills instead of blotter. It would make sense if someone also sold leftover un-pressed powder mix that could be filled into gel caps, for example.
But, again, keep in mind that these pressed pills (and thus the powder they were made from) contained only a fraction of a percent of LSD. Even microdots (which were only 2-3mm in diameter!) would only have been ~1-3% LSD.
Pure LSD is simply too potent to dose in powdered form. The 100µg in a standard "hit" would be a speck of dust so tiny that it would be barely visible to the naked eye.
Look at the microdot on this pic: Yes, this thing is less than 1/10th of an inch across, and yet it contains 7,500(!) micrograms of material.