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.
Like the color of smoky quartz, the color of this type of citrine is caused by irradiation and traces of aluminum built into its crystal framework. The yellow can be very deep with shades of green, but usually is a little pale.