Thank you!

I preface this by saying that I’m just a very amateur hobbyist, and even an expert would never 100% call a stone without physically seeing it, so if you really, really want to know I’d ask a gemologist. The ones in my area throw fairs a few times a year, and I’ve found many jewelers can actually be quite helpful about id-ing a stone, especially if you approach them on a slow day.

But to me the crystals look entirely wrong for agate and don’t seem quite the right shade of green for Prasiolite. The crystals don’t seem quite right in color or shape for Brochantite either.

Aurichalcite is a possibility for the stones in the second pic, although the crystals don’t look as orderly as Aurichalcite usually does.

The left stone in the first pic looks a bit like low-quality beryl, actually. Although I might see banding? Which would be more a calcite or fluorite thing. It’s hard to tell in the photo if it’s actual banding or just light play off broken crystal.

The right stone in the first pic might be chrysocolla, although usually it forms nodules rather than crystals like that. Calcite or fluorite might make more sense for that one too.

Update: most likely Quartz, Azurite, and Malichite, all mixed together to get that weird crystal and color pattern.

Finally got around to talking to a gemologist.

Citric acid is what I use. Easy to find, safe to handle. However, if these aren't copper, and are in fact malachite, you'll be destroying it for nothing.