Silicon based life

The Holy Grail of exobiology.

Life as we know it (again) is carbon based. Carbon bonds with hydrogen and forms various organic compunds, chains, rings, etc.

Silicon bonds with oxygen to form large scale rigid compounds such as rocks. So why not silicon based life? So why not living rocks?

We are already in symbiosis with rocks as "life as we know it" requires a silicon based surface for our carbon based organic molecules to stand on.