The powder you are describing was available in Georgia in the early-mid 70's too. People called it "T" and everyone said it was THC at the time. I bought and used loads of it. Whatever it was...it was not pcp. The tabs that were sold as THC were indeed PCP...at least they had all the effects of that drug. That pill-form pcp was the first drug I ever used besides pot. The effects of 'T' were much different. T seemed much more like a mild hallucinogen of some sort...maybe mescaline, MDA or some derivative. Effects were too short to be acid.
Tom, I don't doubt your story about the girl dying from whatever was in the punch. But I do question whether the agent was either THC (not at all likely for reasons others have stated) or strychnine poisoning. From my research, the whole (& very common) belief that lsd was cut with strychnine was indeed a sort of druggie urban legend.
Here's an article I found on the web that may expain the origin of the myth:
"Strychnine in LSD
This rumor is spread with abandon, explained variously as "strychnine is a by-product of the LSD production process" or "strychnine is used to bind the LSD to the blotter paper" or "LSD is cut with strychnine." Again, there?s little basis in truth for this one. The main argument against this rumor is that active levels of strychnine wouldn?t fit on a piece of blotter paper. There seem to be a couple of mentions of strychnine associated with LSD in the professional literature. One screening test in 1971 showed a trace amount of strychnine in a sample of LSD, but was never verified. Then, in LSD: My Problem Child, Hofmann describes one 1970 case where strychnine powder was sold as LSD, but no LSD was actually involved."