There is no such thing as immaterial matter. All spirit is matter, but it is more fine or pure, and can only be discerned by purer eyes; We cannot see it; but when our bodies are purified we shall see that it is all matter. (Doctrine & Covenants 131:7-8)
Where Is the Spirit World-Is the spirit world here? It is not beyond the sun, but is on this earth that was organized for the people that have lived and that do and will live upon it. No other people can have it, and we can have no other kingdom until we are prepared to inhabit this eternally. (Discourses of Brigham Young, p.376)
Spirits are just as familiar with spirits as bodies are with bodies, though spirits are composed of matter so refined as not to be tangible to this coarser organization. (Discourses of Brigham Young, p.379)
When you lay down this tabernacle, where are you going? Into the spiritual world. ... Where is the spirit world? It is right here. (Discourses of Brigham Young, p.376)
The material world we live in - i.e. those things we can sense through our natural senses, is made of baryonic matter. Baryonic matter includes all atoms and so constitutes virtually everything we can experience. Dark matter, on the other hand, is hypothesized to be non-baryonic. This means that dark matter has absolutely no interaction with normal matter and is completely transparent to electromagnetic radiation. Trillions of dark matter particles could be streaming through your body (and most likely are) and you would sense nothing. They would not interact with atoms in your body and you could not change the dark matter in any fashion.
The only way that the existence of dark matter can be inferred is through the study of gravitational effects such as the rotation speeds of galaxies. Research on distant galactic structures indicates that we can directly sense only about 4% of the mass/energy in the universe. Of the invisible 96%, about 22% is estimated to be dark matter with the remaining 74% consisting of what is termed "dark energy".
Could it be that dark matter and dark energy are the "more fine or pure" spirit world that surrounds us? There is no evidence for such conjecture, but it's an interesting thought experiment.