So-called Chiastolite (a species name discredited some time ago) is a variety of Andalusite containg cross-shaped inclusions of carbon that make the crystals very distinct, for obvious reasons. Somebody went to a lot of trouble and time to make this attractive reference set of thin-sections, cut from the cores of over a dozen crystals. The set was obviously made up to shwo the different patterns possible within, perhaps to better study their formation. Shown in normal light and, dramatically, in backlit lighting.