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.
There are not a lot of rare nickels and they are fairly inexpensive, which makes them a great coin series for the beginner or those with a modest budget to collect. You can put together a nice collection without spending a lot of money. In fact, a lot of the Jefferson Nickel series can still be found in circulation. Who knows, you might even happen across a very unique rare nickel just like Mr. Ken Frith did. In 1961, knowing that Mr. Frith specialized in error coins, a very unique 1942-S Jefferson Nickel was brought to his attention.