I brought up the topic of Fervidite items a while back. The only thing I can tell you regarding items made of Fervidite (and thank you to Statmonkey's reply) is that, like Adamatine, items are definitely harder to hit for sundering purposes (AC 23)
Fervidite thread and it has the added benefit of having even more HP to go through to break them (regarding Weapons and Ammunition). They're granted +50 hp above what the item would normally have and that they're treated like Adamantine & Silver for the purposes of bypassing damage resistances and immunities, or triggering vulnerabilities (pg. 216 of the Arcanis 5e Campaign Setting book).
I do not recall this saying the same for Armors/Shield. Only except regarding Armor made of Fervidite weigh less than usual, removing and Str requirements and Stealth penalties to don them.
I would imagine the same would apply to Armors and Shields made of Fervidite (the AC and HP bonus).