The name “black opal” is used for opal that has a dark body color, often black or dark gray. The term is also used for opal that has a dark blue or a dark green body color. This dark background color makes the “fire” of black opal much more obvious. The contrast of iridescent fire on a…

 Aquamarine is a blue variety of the mineralberyl. It receives its name from its seawater-blue color. It ranges from a very light blue to a deep, richly saturated blue. Most people prefer the richer, more saturated blue gems, and they are the most expensive. Light blue beryls with a low saturation are also called aquamarine. They are…

You have probably not heard of this gem before. Gem silica is a rare variety of greenish blue chalcedony. Small amounts are currently produced in Arizona and a few other locations. It is the rarest and the most expensive variety of chalcedony. Gem silica receives its wonderful color from small amounts of included chrysocolla or copper compounds. It is…

Tanzanite is a violetish blue gem that is only found in commercial amounts in the African nation of Tanzania. Tiffany and Company selected the name to honour the country where it is produced. Tanzanite is a relatively new gem, first discovered in the 1960s, whereas most other popular gems have been known and used for hundreds, if not…

Turquoise is a copper mineral with a bright blue to blue-green color. The color is so familiar and so enjoyed that the word “turquoise” has become a commonly used word for a milky blue-green color. Only a few gemstones have a color that is so familiar. Turquoise is found in dry climates in the rocks above copper deposits. The southwestern states…

Sapphire: Sapphire is a gem variety of the mineralcorundum. When corundum is reddish blue to violet-blue, it is known simply as “sapphire.” Corundums of any other color (except red, which is ruby) are known as “fancy sapphire.” On the basis of dollars spent in the United States, sapphire is the most popular blue stone and the third most…