This is due to several various causes. However, market demand and supply are the two most important factors determining a gemstone's rarity. In most cases, a knowledgeable collector is the one who can predict which gem will be the most sought after by the general public. When discussing gems, the term "availability" relates to how simple or complicated it would be to get that stone.

 Red Diamond

• Diamonds are abundant in nature, and their pricing is dictated by demand and creative marketing by mining firms like De Beers. 

• Rare gems are seldom seen. 

• The rarest birthstone is a red diamond. 

• The most renowned red diamond is the 5.1-carat Moussaieff Red. 

• If this birthstone were auctioned, it would smash the existing record of $71 million for a diamond.

• Diamond has many intriguing tales and qualities.

Red Beryl

• Occasionally, the name bixbite might be used for red beryl. 

• In 1904, a prospector in the Wah-Wah Mountains of Utah stumbled into a rare birthstone. 

• Fine red beryl crystals are seldom faceted since they are reserved for museums. 

• As reported by the Utah Geological Survey, only one red beryl is found for every 150,000 gem-quality diamonds. 

• Beryl is a strong January birthstone with several purported benefits.

Tanzanite

• Geologists from Tiffany & Co. discovered the gemstone tanzanite in 1967

• It was called for the nation where it was first discovered. There is now just a little area in Tanzania where you can get it.

• Thus, supplies are low. Birthstones for December include tanzanite.

Black Opal

• The typical opal will have a light, milky white backdrop. 

• Because of its dark backdrop, black opal boasts the most hypnotic display of rainbow hues. 

• This January birthstone is unique to the arid lands of Australia. 

• Sincerity and generosity are represented by opal, the December birthstone. 

Alexandrite

• In the 1830s, Imperial Russian explorers found alexandrite in the Ural Mountains. 

• Because of its reversible color shift in artificial light, this birthstone is often called "emerald by day, ruby by night." It was named after the Russian Czar Alexander II. 

• Since the Russian mines are depleted, and alexandrite has just recently been discovered in other countries, such as Brazil and East Africa, the gem is tough to come by. 

• Most commercially available alexandrite nowadays is synthetic. 

• Alexandrite is a lucky birthstone since it falls in November.