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.
A blood type is considered rare if fewer than 1 in 1,000 people have them. One of the rarest blood types in the world is Rh-null, which lack any antigens in the Rh system.There are only 9 active donors in the community of rare blood donors that have Rh-null blood. Rh-null is considered a âuniversal bloodâ for anyone with a rare blood type within the Rh system.ne of the rarest blood types in the world is Rh-null, which lack any antigens in the Rh system. There are only 9 active donors in the community of rare blood donors that have Rh-null blood.