Well you didn't really specify much of anything, your character just grabbed a big rock and slammed it down on top of the Mech. As you can see in the picture though, the rock would slam into the upper lens first, absorbing most of the shock, as the rock would essentially break on contact with the metal. If anything was going to break, it would be that upper lens. 

You also have to look at the exact composition of the Mech's armour, which I hadn't bothered to mention up until now because I forgot all the nifty MBT research I did before making this character. Its armour is made up of titanium and depleted uranium with aluminium tiles worked in, it's based off Chobham armour, which is specifically designed to reduce the effect of kinetic impacts by displacing the energy over tiles. It's easy to imagine the Mech as just a big suit of armour with a man inside representing the internals, but it's not. The armour is incredibly advanced and designed to stop penetration from anti-tank rounds, even the Optics armour has incredibly high resistance. Any impact which is caught by the armour should have limited effectiveness, that's how the Mech is designed. No matter how strong your character may be, you would not expect it to penetrate the front of a tiger tank with a rock, and that's exactly what it tried to do. The only question is what shock would transfer through the armour, which considering its composition I believe would be minimal, and considering the Optics are designed for use in a vehicle that is used in warfare (and therefore expected to be affected by shocks, such as anti-tank rounds colliding with the Mech) I found it highly unlikely the Lens would shatter from an indirect attack.

Also, Innue has pneumonia so we might have to ask Pollen to have a look if we want a prompt decision.