||The amount of powder neccessary for a significant dose of mescaline is typically more than what's contained in a "microdot" or other small pills touted as mescaline. Mescaline is active in the 200+ milligram range and requires a normal sized gelcap or large sized pressed pill to contain this much material. A common dose of LSD is 100-200 micrograms which can easily fit in a small tablet.|
The general lack of synthetic or extracted and purified mescaline on the black market makes it likely that many things sold as mescaline will be something else. There is no easy way to test or determine the difference quantitatively. LSD can be experientially different from differing sources/batches, and its quite possible to mold or recall a trip to be akin to a description of a mescaline trip.
You may want to read up on a pure mescaline trip report in PiHKAL (listed under "M", by Alexander Shulgin) or page 96 of Pharmacotheon by Jonathon Ott.