Mystery opi accidental extraction?

Bonjour,

So for harm reduction I like to give back to my community n wash peoples stuff. I was tasked with cleaning a bunch of resin/foil runoff just incase it had dirt etc in it

I did a distilled water filtration, and there was some stuff in there that wouldn't dissolve even when heated. I assumed it was dirt, but then the remaining mannitol rock didn't have any effect noticeable (or even stop wd)

So I looked at this "dirt", and thought I'd isopropyl extract it incase the f/rc was freebase or smth, but it didn't dissolve

I tried water, acetone, and isopropyl alcohol and nothing.

Looking to make 'em a safe smokable version, or worst case scenario a vape juice, as nasal and iv is too risky

TL;DR: What rc opioid is insoluble in those, and is brown almost like H? And what is a safe dose & way to prepare it for an "old school H high-tolerance" type dude?

Love you xxx

Inb4 "it was bunk" or "#3" I know it came from good stuff and would've recognised #3 if someone was smoking it a mile away