I realize that many of these terms, such as fertile darkness, luminous blackness, alive luminosity, crystal clear quality, and so on, can be seen as poetic inventions. In a way, they are, but they are also what seems closest to immediate experience.
There is an immediate experience of the fertile smooth rich darkness, the alive luminosity, the luminous blackness, the crystal clear quality, and more. These are the terms that are most close to how each of these appear, when arising in awareness.
They are metaphors, but the closest to experience that we, or at least I, can get. The words themselves come from the thinking mind, but the thinking mind is only of assistance in putting it into words, as close to experience as possible. It has a secondary and minor role. Experience is primary, putting it into words secondary.
Emptiness filtered through head and belly centers
For instance, emptiness, then filtered through the head center, or even thought about in abstract terms, could be called fertile. But it is a stretch. Its empty quality is in the foreground, and the empty quality of all forms are in the foreground. The experience is that forms are emptiness, that they are inseparable. To say that form comes out of emptiness, and emptiness in that way is fertile, is possible, but a stretch from the immediate experience. It is an intellectualization.
But emptiness, when filtered through the belly center, does have a sense of fertility about it. It is black smooth full rich and fertile, and a fertile ground of form. In our immediate experience, it appears as fertile, as brimming with potentiality.
So to call emptiness fertile is more of an intellectualization if filtered through the head center, and an immediate experience when filtered through the belly center.