Here's why:

* Dolerite is an igneous rock. This means it formed from cooled magma or lava.

* Igneous rocks are generally opaque. They are composed of tightly packed crystals, which block the passage of light.

* Dolerite is often dark in color. This is due to the presence of minerals like pyroxene and olivine, which absorb light.

While light might pass through very thin slices of dolerite, it won't be visible to the naked eye.