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.
Color. Citrineâs attractive color, plus the durability and affordability it shares with most other quartzes, makes it the top-selling yellow-to-orange gem.itrineâs colors range from pale brownish yellow shades like this one to intense reddish orange hues. - Robert Weldon. This fantasy-cut citrine started out as an amethyst. Its orange hues are the result of low-temperature heat treatment.