As a gemstone expert with extensive knowledge in the field of mineralogy and gemology, I can provide you with an informed answer regarding the rarity of gemstones.

The title of the "rarest gemstone in the world" is a subject of some debate, as rarity can be measured in different ways, including the number of specimens found, the difficulty of obtaining them, and their availability on the market. However, one gemstone that is often cited as being among the rarest is the red diamond.

Red diamonds are incredibly rare, and only a few have been found in the world. They are so rare that they are almost never seen on the market. The red color is caused by a unique atomic structure that is not fully understood, and it is this scarcity and mystery that make red diamonds so valuable.

Another contender for the title is the painite. It was first discovered in 1955 and was so rare that it was only found as a single specimen in nature for many years. It has since been found in larger quantities, but it remains a rare and valuable gemstone.

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The following 10 gems are the world's rarest and most valuable gemstones.Poudretteite. First discovered in the 1960s in the Poudrette quarry of Mon Saint Hilaire, Quebec, Poudretteite is one of the rarest gems known today.Tanzanite. ... Benitoite. ... Grandidierite. ... Black Opal. ... Red Beryl. ... Jadeite. ... Taaffeite.More items...read more >>