Tourmaline

Lord Juss sat in the high seat midmost of the dais, with Goldry on his right in the seat of black opal, and on his left Spitfire, throned on the alexandrite. On the dais sat likewise those other lords of Demonland, and the guests of lower degree thronged the benches and the polished tables as the wide doors opened on their silver hinges, and the Ambassador with pomp and ceremony paced up the shining floor of marble and green tourmaline.

Source: tatoeba (8863887)

If from a transparent prism of tourmaline two thin plates are cut, parallel to its axis, they will transmit light when they are placed above each other with the chief axis of each in the same direction.

Source: tatoeba (11580297)

The garnets in the detritus are accompanied by zircon, spinel, corundum, cyanite, tourmaline, olivine, etc.

Source: tatoeba (12351523)

The floor of the chamber was tesselated, of marble and green tourmaline, and on every square of tourmaline was carven the image of a fish: as the dolphin, the conger, the cat-fish, the salmon, the tunny, the squid, and other wonders of the deep.

Source: wiktionary