Fire Opal – $2,300 per carat

 

Black Opal (Credit: Bonhams Ltd)

Black Opal (Credit: Bonhams Ltd)

Fire Opal (SiO2·nH2O) is actually not technically a mineral but instead is a mineraloid. The reason being opal does not have a crystal structure that is required for all minerals. As noted in the chemical formula, opal is a hydrated form of silica or silicon dioxide. Opals can form in a variety of different colors depending on the environmental conditions during formation. The mineralogy of opal allows it to diffract light, causing it to shimmer various colors.

Poudretteite – $3,000 per carat

 

Poudretteite (Credit: Smithsonian Gem Collection)

Poudretteite (Credit: Smithsonian Gem Collection)

Poudretteite (KNa2B3Si12O30) was originally discovered in Mont St. Hilaire Quebec, Canada in the 1960s by the Poudrette family. The gem is naturally pink in color and has a Mohs hardness of 5. It wasn’t until 2000 until the first gem quality poudretteite was found in Mogok, Burma at an amazing 9.41 carats (pictured above).

Alexandrite – $12,000 per carat

 

Alexandrite (Credit: daysjewelers.com)

Alexandrite (Credit: daysjewelers.com)

Alexandrite (BeAl2O4) is a type of chrysoberyl that was found in the Ural Mountains, Russia in the 1830’s. You may have seen the incredible changing color of this mineral where it appears to be emerald in light and ruby red in darkness. The difference between alexandrite and chrysoberyl is the presence of iron, titanium, and chromium as impurities within alexandrite.