On Lithobiology and Crystalloecology
From the files of Aran Neylis, self-proclaimed 'scholar of the world' and Priest of Ioun.
The discerning adventurous soul has, no doubt, encountered or at least become aware of the staggering variety of biological forms that beings--sapient and nonsapient--can take in this grand cosmos of ours. Some brought to life through divine artifice, arcane experimentation, the twisted influence of para-real entities, natural confluences of magic, or a host of other sources. Life, put simply, is everywhere, in every form it can find, no matter how alien it may seem to the inexperienced eye. Yet some forms still manage to surprise, and perhaps foremost among these are those of lithobiological persuasion: forms of, quite literally, living rock.
Lithobiological entities tend to form in places where the erosion of their body material is, if not less likely, then at least less intense. I have noted a profound preference among shardminds for places that are hot and dry, as cool climes invite erosive forces like ice or lichen, while hotter ones generally discourage anything but wind, which can be relatively easily warded off. Such locations also tend to have far less competition from non-lithic organisms, creating a viable niche for various lithic species to occupy.
As is the case with enfleshed life, ecological structures form with resource-consolidators at the bottom and consumers at the top, but the mechanisms and relationships can be quite different. Unlike plants, which depend primarily on Pelor's radiant bounty, lithic plant-equivalents depend much more on the physical materials in their environment. Water is both enemy and ally here; too little and the faster crystal-growing forms of lithic life cannot take hold, and the slower, more independent metamorphic-based life flourishes. Hence, often you will see crystalloecology manifest most strongly in areas that are otherwise dry, but have a minimal source of highly mineral-rich waters; geysers and calderas are the major examples, especially those in or adjacent to arid-desert regions.
The precise mix of minerals present in a location can have a profound effect on the appearance and ecological structure of such crystalline enclaves. In places where corundum is abundant, brilliant hues of red, blue, green, and yellow manifest, and these hues often infuse up the crystalline food chain, as rubies and sapphires are plucked from the fumaroles to feed higher-order crystalline life. Sapient crystalline beings sometimes even selectively consume crystals of specific color and intensity so as to alter their body color. To the best of my knowledge, this is simply a preference or cultural expression, but multiple individuals I have intervewed were insistent that red-colored individuals move at greater speed than other hues. Alas, populations being as small as they are, true testing is not possible at this time.
A selection of lithobiological creatures, and an attempt at a "taxonomic" classification, follows...