Is it defined that inert objects by our scientific subjection of them being non-living have no consciousness at all? If that be so, what about viruses? And how would a rock's consciousness differ from a) a Golgi body(organelle) and b)Plasmodium ( a single-celled organism)
Brahman is by it's nature consciousness, it permeates everything. Krishna says in the Gita - "That by which all this is pervaded know to be imperishable.." (Gita 2.17) and "And whatever things there be...know they are from me alone. I am not, however, in them; they are all in me." (Gita 7.12) In other words, Brahman, ultimate consciousness, permeates everything and everything exists in Brahman, but from a relative standpoint, all things do not have a relative consciousness and all beings are not aware of their ultimate consciousness.
Just like there is a "critical mass" required to have a nuclear bomb, there is a "critical number of neurons" required for an organism to be conscious (self-aware). although the minimum number has not been established, I would estimate the number should be greater than a million. Based on this, a rock has no consciousness because it has zero neurons. Also, one-cell organisms and up to viruses, have no consciousness, because they don't have enough neurons.