Not really impressed with Iridium plugs
They were Champions, I did check the gap when installed, but I didn't see any evidence of the iridium part breaking, just worn down.
The iridium core in the "positive" anode is not meant to be wear resistant, it is designed to be misfire resistant to wear and possible fouling due to less than optimum eng.
conditions. The material is supposed to promote a superior conductivity that encourages the spark to prefer it and the "jump" to taking the fouled/contaminated ceramic to
ground, especially important under high cyl. pressures and lean conditions which make it harder for the spark to jump.
I have been seeing a number of plug failures in the last few years, even OE ones from reputable mfrs., including the anode separating and dropping down resting nicely on
the ground. Some have dropped the ceramic cone, and it sits there like a little shroud, lol! Most of these are newer, smaller designs to accommodate the tight fit in some
of these new chamber/valve configurations, esp Direct Injection units............................
Is there anything left visible in the core of the ceramic of the "missing" anode if You bend/cut the ground out of the way? That does look like evidence of an unwelcome
guest in that shot of the piston, it could have failed and still burned at the fracture until it plasma'd itself off & fell in.................