This is the third paper from Addadi et al on guanine crystals in koi skin. In the first they SEM image iridophores and through spectroscopy determined that the guanine crystal platelets in koi iridophores were anhydrous guanine. In the second paper they more exactly sized the measurements of the crystal stacks and cytoplasm in-between. In the third paper they describe the amorphous substance from which the crystals form and discuss how the individual platelets grow flat contrary to their usual habit. There are some electron microscope close-ups of gin rin. A fourth paper is promised, but may not be immediately forthcoming, it will look at metallic iridophores. This would be an important extension of the previous research. And it would go a long way toward eliminating the ambiguity that the selection of specimens introduces. They used ogon and gin rin ogon and this introduces some uncertainty as to the micrographs being of gin rin or hikarimono. If a fourth paper deals with this issue then the selection of ogon and gin rin ogon was actually quite astute.
http://departments.agri.huji.ac.il/animal/staff/faculty_staff/sivan_berta/publications/40-Gur-etal-2012.pdf