Most Total Time Spent in Space. Soviet cosmonaut Sergei Krikalev holds this record, with a little more than 803 days accrued over six spaceflights. That's more than two years and two months spent zipping around the Earth.
Natural citrines are rare. Most commercial citrine is heat-treated amethyst or smoky quartz. Because the color is now caused by finely distributed iron minerals (mostly hematite and goethite), heated amethyst is not a citrine in the strict sense.Quartz colored by inclusions of any kind is not called a citrine.atural citrines are rare. Most commercial citrine is heat-treated amethyst or smoky quartz. Because the color is now caused by finely distributed iron minerals (mostly hematite and goethite), heated amethyst is not a citrine in the strict sense. Quartz colored by inclusions of any kind is not called a citrine.
See the birthstone tables for additional references to this stone or citrine jewelry. Citrine is a variety of quartz ranging in colors of yellow, yellow-brown, orange, dark orange-brown, reddish-brown. Citrine crystals can form together with amethyst or smoky quartz to form a bi-colored quartz called ametrine.Almost all citrine that is available on the market today is heat-treated amethyst.ee the birthstone tables for additional references to this stone or citrine jewelry. Citrine is a variety of quartz ranging in colors of yellow, yellow-brown, orange, dark orange-brown, reddish-brown. Citrine crystals can form together with amethyst or smoky quartz to form a bi-colored quartz called ametrine.