Chiastolite

Chi‐as″to‐lite (kī̍‐ăs″tō̍‐līt), n. [Gr. χιαστόσ marked with a χ + -lite. See Chiasm. So called from the resemblance of the cross cuts of its crystals to the Greek letter χ.] (Min.) A variety of andalusite; — called also macle. The tessellated appearance of a cross section is due to the symmetrical arrangement of impurities in the crystal.