can you tell me why scientists are looking for dark matter down a coal mine?
When what it is that they are looking for is not matter.
I believe it is know as the fabric of space.
Dark matter is unseen matter in the universe. We know it is there by the observed gravitational effects on other galaxies, but wen cannot see it because it does not emit light. Interstellar dust and gas are other forms of dark matter.
I think you are talking about neutrinos, which are everywhere and extremely abundant. If they have mass, then these subatomic particles could account for the missing dark matter. Trillions of neutrinos pass through your body each second from space; they are, or nearly are, massless and very weakly interacting with other matter, so they can pass through the earth. A neutrino detector must be built underground so that it is shielded from the other particles from space. That is why neutrino detectors are built in abandoned mines. Latest experiments show that they can change form; therefore, they must have some mass, albeit very tiny compared to other particles.