gem edge weapons are pretty silly. Do they bring it to the local laser cutting machine or what?
Gem arrowheads, maybe, but pretty wasteful. I don't see them being particularly more effective than flint.
Flint (or other kinds of chert) are great and effective for anything from arrows up to fairly large axes. Not swords though, much too brittle to extend torque out like that. Axes, hammers, and spear points are compact in size and thus won't shatter.
Glass is fine too, but is a hell of a lot more effort than chert for weapons for no benefit in strength, and is not exactly a low tech alternative to metals.
Obsidian is similar to chert
Hammers are super easy to make out of damn near anything and would be plenty effective. Most rocks are fairly similar in density, but if you still want to max out density for a hammer, igneous rocks are generally the heaviest, specifically mafic igneous rocks like basalt.
None of the above are appropriate at all for armor. If you want low tech armor, your best bet is cloth armor, which can be extremely protective and sturdy. It's also, incidentally, the best kind of armor against bludgeoning (better than steel! In real life, dunno about DF) which, if you're in a stone age fight, is probably pretty important. And with many thick layers, pretty resistant to edges too. Not cheap for a low tech people to make, but doable.
Ceramic, no. It shatters from a stern look if it's thin enough to be sharp, and those are mostly very modern ceramics anyway. Old world ceramics would nearly always be lower quality (silt impurities for instance) and need to be tempered with grog or shells or similar which makes any kind of edge totally impossible, and simply aren't composed of the same exotic materials.