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.
We know that A, B, AB and O are the four blood groups that can be Rh positive or negative (viz: A+, A-, B+, B-, AB+, AB-, O+ and O-). Among them, O+ is the most common; while AB-is the rarest blood type.The detailed explanation provided here will help in better understanding of the subject.B-and B-are the rarest blood types in the world. The Bombay blood group (hh), a relatively unknown blood type, is also one of the most uncommon blood types in the world. Little is known about the Bombay blood group (hh) , one of the most uncommon blood group in the world.