Complex sentence: It is found as well-developed crystals, but there are most often poorly terminated, and are of a bright hyacinth-red color, which are translucent and have an adamantine to vitreous lustre.
Split into simpler sentences: It is found as well-developed crystals, although these are usually poorly terminated. Crystals are of a bright hyacinth-red color, translucent, and have an adamantine to vitreous lustre.