A few days ago, I was out taking some photos with my new Hoya HD CPL. Many reviews rate it as unbreakable. You cant even scratch it even if you bang it against sharp objects. check this demo out and you'll be convinced that its super dam tough.
Anyways after taking some photos, I noticed some 'dust' particles hovering around in the images. I thought, hey maybe its snow or smth... So I took out my cleaning cloth and attempted to wipe them off the filter. Low and behold, what I saw next almost gave me a heart attack.
Lesson learnt, nothing is indestructable.
I'm pretty sure that impact didn't cause the filter to crack as I didn't hit it or bump into anything. The prime suspect is the cold weather, it was -10C that day so the repeated drastic change in temperatures of hopping onto and off buses could have caused a reduction in the fracture toughness of the filter. But i'm not sure.. Any thoughts on this guys?