Bone

Bone can be used in place of wood and steel in weapons and armor.

Source: Pathfinder Roleplaying Game Ultimate Combat

Other animal-based materials like horn, shell, and ivory also use the rules for bone weapon and armor. The cost of a bone weapon or bone armor is half the price of a normal weapon or armor of its type.

Weapons

Light and one-handed melee weapons, as well as two-handed weapons that deal bludgeoning damage only, can be crafted from bone. Hafted two-handed weapons such as spears can be crafted with bone tips, as can arrowheads. Other two-handed weapons cannot be constructed of bone. Bone weapons have half the hardness of their base weapons and have the fragile weapon quality. masterwork bone weapons also have the fragile quality, but magic bone weapons do not. Bone weapons take a –2 penalty on damage rolls (minimum 1 damage).

Armor

Studded leather, scale mail, breastplates, and wooden shields can all be constructed using bone. Bone either replaces the metal components of the armor, or in the case of wooden shields, large pieces of bone or shell replace the wood. Bone armor has a hardness of 5 and has the fragile armor quality. masterwork bone armor also has the fragile quality, but magic bone armor does not. The armor/shield bonus of bone armor is reduced by 1, but in the case of studded leather, the armor check penalty is also reduced by 1 (to 0).

Fragile Weapon & Armor Quality  

Source: Pathfinder Roleplaying Game Ultimate Combat  

Fragile weapons and armor cannot take the beating that sturdier weapons can. A fragile weapon gains the broken condition if the wielder rolls a natural 1 on an attack roll with the weapon. If a fragile weapon is already broken, the roll of a natural 1 destroys it instead.  

Armor with the fragile quality falls apart when hit with heavy blows. If an attacker hits a creature wearing fragile armor with an attack roll of a natural 20 and confirms the critical hit (even if the creature is immune to critical hits), the armor gains the broken condition. If already broken, the armor is destroyed instead. Fragile armor is not broken or destroyed by critical threats that are not generated by natural 20s, so if a creature wielding a weapon with a 19-20 or 18-20 critical range scores a critical hit on the wearer of this armor with a roll of less than a natural 20, that critical hit has no chance to break or destroy the armor.

Masterwork and magical fragile weapons and armor lack these flaws unless otherwise noted in the item description or the special material description.