Alexandrite

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.

As the colors green and red are the national colors of Russia, and the date of discovery of this stone in Russia occurred on the Emperor’s birthday, the name alexandrite was given to this species of chrysoberyl.

[…] the body of each high seat was a single jewel of monstrous size: the left-hand seat a black opal, asparkle with steel-blue fire, the next a fire-opal, as it were a burning coal, the third seat an alexandrite, purple like wine by night but deep sea-green by day.