Can we even refute that a rock is conscious? That philosophical zombies are possible? Does consciousness have any experimental basis beyond that we all say we feel it?
Let's go with the dictionary one for starters: "the state of being aware of and responsive to one's surroundings.".
The rock is neither "aware" nor "responsive". It just stands there. It's a non-reactive set of minerals, lacking not just any capacity to react, but also life.
Though that's overthinking it. Sometimes you don't need decicated testing equipment to know something, just common sense.
Consciousness and responsiveness are orthogonal. Your dictionary would define the locked-in victims of apparently vegetative states as nonconscious. They are not.
Common sense is valuable, but it has a mixed scientific track record.