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.
Citrine is the yellow to brownish-red variety of the mineral Quartz. It is a widely used as a gemstone, and after Amethyst it is the most popular Quartz gem. Most Citrine is formed by heat treating purple Amethyst. Citrine may also be produced by heat-treating Smoky Quartz from certain localities.atural light yellow Citrine is often called Lemon Quartz on the gemstone market. Sometimes Citrine has a smoky hue to it, and can be borderlined between Citrine and Smoky Quartz, with either definition being correct. For additional information, see the gemstone section on Citrine.