Coming in late is no problem for me.

"Sand" is the best term I could come up with. It's really quartz crystals (i.e. sand) but is includes green and blue particles that are the same color as the "specks" in the finish. I'm not sure what tradename the finish is since it was before my time, but it's an aggregate of quartz crystals - mostly white, but with blue and green crystals in it as well. If it was just sand, I'd be looking for an external source, but the presence of the green/blue particles (in what I see on the bottom of the pool and what I wash out of the cartridge filter) convinces me it's the pool finish. Also, if I brush with a SS brush, I can get a small pile of the stuff below the brushing area.

I was using Tri-chlor tabs from Sam's Club (which I believe are a recommended brand if you are going to use Tri-chol); but I have switched to Cal-Hypo (while I raise my CH a bit) and Liquid Chlorine - so it's not that. No sand filter or kids with a sand box, but it is sandy soil for sure.

Like I told Doc, my pH was below 6.8 for an unknown length of time and CH was 180 or less as well - before I found this site.

I'm hoping having my water balanced on the slightly + side of the SI scale will eventually stop this from happening. It does seem to have slowed.
John