Chiastolite
Chiastolite (ki*as"to*līt) , noun
[Greek chiasto`s marked with a χ + -lite. See Chiasm. So called from the resemblance of the cross cuts of its crystals to the Greek letter χ.]
(Mineralogy) 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.