chal·ced·o·ny also cal·ced·o·ny 
(kăl-sĕdn-ē)
(kăl-sĕdn-ē)n. pl. chal·ced·o·nies also cal·ced·o·nies
A translucent to transparent milky or grayish quartz with distinctive microscopic crystals arranged in slender fibers in parallel bands.
[Late Latin chalcēdonius, from Greek khalkēdōn, a mystical stone (Revelation 21:19), perhaps from Khalkēdōn, Chalcedon.]
chal′ce·donic (kăl′sĭ-dŏnĭk) adj.