"Fire from a Rock"
Smoke represents the burning desire of man to escape the confines of corporeal existence, and ascend upwards to fuse with his Creator.
Normally, smoke can only be made when there is some "fuel," present, be it animal or mineral.
But, at Mount Sinai, God made a "consuming fire" which emanated from the mountain itself - fire from a rock.
This teaches us that we need to bring enthusiasm even to the dreary, "inanimate" parts of our lives. A person may think that excitement - love and fear of God - are to be reserved for the Synagogue or for Torah study. But when it comes to petty chores and simple, mundane acts, these are totally disconnected from any higher purpose.
Not so! Remember that at Mount Sinai, even the rock burned. So too, even' the most dreary and mundane acts can be brought alive with the fire and energy of Torah inspiration.