Update on these ideas:
I guess the only Irish thing I would have with Gaelic civ is the shillelagh, and this is accomplished with the brogit staff, so that civ can just be Scottish.
Looking more closely at native Australian weapons, I probably could do a wallaby civ without combining in Polynesian or Maori to get a full arsenal. I want to share some pics of what I found:
Obviously, the flying boomerang as their ranged weapon:
The "number 7 boomerang" or "leangle club" melee weapon:
Barbed spears:
The waddy mace:
And the impressive "sword club" which is absolutely my new favorite thing:
There is also the distinctive parrying shield:
Unfortunately, to my knowledge, DF does not have a way to achieve weapons that are good at parrying or shields that are good at bashing, but I might include this as punching weapon, like a katar. "Rule of Cool"
The cool thing is that a lot of these are basically edged weapons, so assuming they have access to metal in Furry Fortress, a lot of these boomerang things are basically sword and axe equivalents.
This means there cultural metal would probably be some sort of hardened wood.
The Maori definitely have enough distinctive native arms that they could stand alone with combining with Polynesia. Their civ animal would obviously be a kiwi, kea or kakapo. Although, I do have a soft spot for NZ's 100 year old, poison blooded, man eating eels. And the weta. As Nahere said, some reference to pounamu (which I know as "greenstone") would be a must.
Polynesia certainly has enough weapon shapes to stand alone, but naming them might get tricky. Their civ animal would probably some generic sea creature, first on my mind is a sea horse. (and I know you're thinking it, Leafy Sea Dragons are Australians, and wallabies got dibs) Again, some sort of wood+teeth material.
As for more weapons-grade stone, some article suggested that the Aztec macuahuitl could be considered analogous to modern ceramic knives, and I saw that modern ceramic knives are typically made of Zicronia, ZrO
2. I am unclear on how this material is synthesized, but it apparently occurs in nature as the mineral Baddeleyite, so I don't feel bad about making it a naturally occurring type of weapons grade stone, like obsidian is. Other weapons grade stone could be the aforementioned jadeite/greenstone/pounamu (which I think are all chemically the same thing). Baked silcrete was used to make stone tools, I'm not sure I would force players to bake it though, since this mean an extra step to get a material that is still inferior to obsidian, jadeite or, oh yeah, metal, and I'm assuming it works at kitchen temps rather than smelting temps anyways, which the game already eschews. Chert can also yield flint formations. I've also seen stone tools made of quartzite, basalt and rhyolite, but this is probably not worth bothering with.
Still trying to think about ways to handle Neutronium too. So, assuming that native Neutronium is useless (a 10-ton marble), you need to reduce its density by combining it with something. A fun thought I had was that maybe Neutronium is held "in stasis" by tetravalent element, mainly carbon, possibly silicon. In this case, you could render different forms of useful neutron by combining it with different forms of carbon, Nu + charcoal = Neutronium Carbide, Nu + diamond = Neutron Diamond, Nu + graphite = Neutron Paper (heavy graphene). Neutronium Carbide could be alloyed with iron to produce Neutron Steel. If silica works as a tetravalent compound (and since I'm already bending science over the table, why not?), you could make Neutron Sand and therefore Neutron Glass. (except that I don't actually know how to add types of glass)