In the Stargate Atlantis fifth season episode "Remnants", a device is found whose purpose was to seed a planet with silicon-based life.

Four-legged creatures of solid crystal, they're predators, but not particularly harmful to carbon-based life, since they can only digest other silicon-based life.

But he's supposed to be an expert on silicon-based life, and I want to know where this thing came from.

Since the advent of the microprocessor in the late 1960s, these machines are often classed as "silicon-based life".

And we have encountered silicon-based life before.

Set in the Humanx Commonwealth, Prism is a unique planet because its ecosystem contains both silicon-based and carbon-based life.

Just as the lower forms produced Humanity, so they in turn produced silicon-based life, the metal intelligences.

Or they always told us in xenobiology that it would be, if silicon-based life was ever discovered.

The most frequently mentioned alternative to carbon is silicon-based life, while ammonia is sometimes suggested as an alternative solvent to water.

Nonetheless, in certain conceivable planetary environments, some form of silicon-based life might be feasible.