Rock Review: Opal

Today’s Rock Review highlights the Opal, October’s birthstone.

Geology Buzz

Opal gets its name from the Latin word, “Opalus” meaning precious jewel. Opal is a non crystallized version of Silica that formed where ancient boiling hot springs existed in prehistoric times. As the springs dried up, Silica chemically combined with water and became lodged in cracks of the earth’s surface. Opal’s actually still contain some water, up to twenty-one percent. That is why it’s important to carefully guard it from heat and chemicals that can react with the water, causing cracking and loss of iridescence. It is a five to six on Mohs scale of hardness, so it must be shielded from blows as well.

The structure of the Opal is what makes it diffract light and have its unique internal play of iridescence. It consists of Silica spheres that exist in hexagonal or cubic lattices. The conditions under which an Opal forms determines its color. Most Opals are a mottled clear to gray, however, more exotic colors such as red, blue, pink, green, yellow, brown and black have been found as well, black being the rarest.

Fun Facts

Legend has it that the Opal fell from heaven with a bolt of lightning. Ancient cultures valued Opals for their ability to ward off evil and guard eyesight from damage. Nobility often wore them in crowns and as necklaces for security. They were even used medicinally ground up and ingested for healing and to protect from nightmares. Thankfully we don’t use our Opals in this way anymore.

Ninety-seven percent of the world Opals come from Australia, which is why it’s the official gemstone of the country. More recently, common Opals have begun to be valued for use in the jewelry market as well as precious Opal. Some fun common Opal options to consider are the Milk Opal in milky white and the Peruvian Opal in pink and blue. There is less iridescence in common Opals, but still some unique mottled colors that make them quite beautiful. Giving Opals as a gift symbolizes faithfulness and confidence. What a great message for lucky Birthday guys and gals this month!

Rock Review: Dendritic Opal

In today’s rock review will take a look at an “international gem of mystery”, the Dendritic Opal. It is found across the globe, and colors range in many neutral tones, from tans to grays often mottled with white. Part of what makes Dendritic Opal so beautiful is its dark branching formations called dendrites. They appear to be similar to moss or roots giving it a unique look that many people think is reminiscent of a fossil! However, the dendrite branches actually come from the mineral Manganese rather than fossilized plant life.

Luckily for Opal lovers, it is easy to maintain the gem at home since it can be cleaned with a simple dish soap and warm water solution then thoroughly dried with a soft cloth. Many people have long enjoyed Dendritic Opal for its metaphysical properties of promoting spiritual growth. It also is a popular gem with healers, aiding in treatment of blood, breathing and skin disorders. The famous Carl Faberge (think Feberge Egg) was a fan of Dendritic Opal and used it in a number of his pieces, some of which were supplied to the Russian imperial court. Many gem lovers in the 21^st century are still enjoying Dendritic Opal for its unique marriage of rocky and organic looks.

Some confusion surrounds the stone’s identity and make up due to some aliases sometimes given to doppelgangers of this gem. For instance Dendritic Opal is often referred to as Merlinite which is actually a Chalcedony. Merlinite was dubbed an “Opal” because of its opalescence, but is not in fact an Opal. Agates with dendritic features are also sometimes labeled Dendritic Opal, but also are not authentic Opals. A true Dendritic Opal IS a common Opal, meaning it has no play of color, that also has the presence of dendrite formations.

Check out this lovely piece from Layne Designs in Dendritic Opal!

Dendritic Opal Ring from Layne Designs