Southern Jewelry News
  • Featured
    • All
    • Featured
    • Featured Retailers
    • Retailer Roundtable
    • Sponsored Content
    • Supplier Spotlight
    Father’s wisdom takes NM jeweler to fourth generation
    Young Jewelers, a mainstay in downtown Jasper, Alabama for 75 years.
    75 years Young: Strong women always innovating
    An Ocean Full of Diamonds
    RDI Diamonds provides business solutions for independent jewelers
  • Latest News
    • All
    • COVID-19
    • Furry Friends
    • Industry Awards
    • Industry Events
    • NRF
    • On The Move
    • Other News
    • Tradeshow News
    • Video
    • What's New
    jewelers Security Alliance logo
    JSA offers recommendations for what to do in a robbery
    Ethical Metalsmiths announces launch of Grantorship Program
    Jewelers Mutual® Group celebrates 110 years
    Twenty-Four Karat Club New York hosts 120th Annual Banquet
  • Podcast
  • Columnists
    Image of Chuck Koehler
    The Retailer’s Perspective: Just Say No! If You Can
    The Story Behind the Stone: The Wonder of it All
    Is the customer always right?
    Successful Custom: Stressing the bench jeweler
    The Story Behind the Stone: Diamonds on Pins and Needles
    Jewelry Marketing Survival Guide
    The Story Behind the Stone: Out of the Blue
    What’s Hot Now!: Latest Designer Trends 2023
    A Winning Strategy: How SEO and buying intent can skyrocket your sales
  • Classifieds
  • Subscriptions
    • Newsletter Signup
    • Print Subscription
No Result
View All Result
Southern Jewelry News
  • Featured
    • All
    • Featured
    • Featured Retailers
    • Retailer Roundtable
    • Sponsored Content
    • Supplier Spotlight
    Father’s wisdom takes NM jeweler to fourth generation
    Young Jewelers, a mainstay in downtown Jasper, Alabama for 75 years.
    75 years Young: Strong women always innovating
    An Ocean Full of Diamonds
    RDI Diamonds provides business solutions for independent jewelers
  • Latest News
    • All
    • COVID-19
    • Furry Friends
    • Industry Awards
    • Industry Events
    • NRF
    • On The Move
    • Other News
    • Tradeshow News
    • Video
    • What's New
    jewelers Security Alliance logo
    JSA offers recommendations for what to do in a robbery
    Ethical Metalsmiths announces launch of Grantorship Program
    Jewelers Mutual® Group celebrates 110 years
    Twenty-Four Karat Club New York hosts 120th Annual Banquet
  • Podcast
  • Columnists
    Image of Chuck Koehler
    The Retailer’s Perspective: Just Say No! If You Can
    The Story Behind the Stone: The Wonder of it All
    Is the customer always right?
    Successful Custom: Stressing the bench jeweler
    The Story Behind the Stone: Diamonds on Pins and Needles
    Jewelry Marketing Survival Guide
    The Story Behind the Stone: Out of the Blue
    What’s Hot Now!: Latest Designer Trends 2023
    A Winning Strategy: How SEO and buying intent can skyrocket your sales
  • Classifieds
  • Subscriptions
    • Newsletter Signup
    • Print Subscription
No Result
View All Result
Southern Jewelry News
No Result
View All Result
Home Columnists

International School of Gemology Education Series: The Story of Opal

Robert James FGA, GG by Robert James FGA, GG
January 2, 2023
Share on FacebookShare on Twitter
Reading Time: 7 minutes

Opal is a gemological study all its own that can last a lifetime. There are many classifications of opal, far more than we can go into here. If you are going to buy and sell opals as a dealer, you will need a lot of experience in the valuation of opals. You also need to know the basics of how to identify opals as natural, from a gemological standpoint.

Perhaps most important, you will need a lot of experience in the wide varieties of types, grades and colors of opals because small variations in color or formation can account for wide variables in value, particularly if you want to appraise opals. Don’t think you are going to be able to go to The Guide, or some other industry publication, and get enough pricing information to appraise a fine quality opal. It just won’t happen. Opal appraising should be done by those who have heavy experience in the opal markets, and/or have a lot of friends that deal in opals.

Formation

Opals occur due to silicon rich ground water seeping into voids left by decaying ancient trees, or seeping into fissures of existing rock. Although other types of created underground voids can cause opalization to occur, the decaying forest and rock fissures are the places where many opals form. As the cellulose of the tree wood decays, it leaves empty cells in the wood. As the silicon-rich water seeps down into the void, it eventually dries out and leaves the silicon behind to form opals. Some of the water is retained by the silicon dioxide, which is why opals contain water, averaging between 10% and 15%. The silicon forms into small rows of round spheres that create the classic play of color, a diffraction of light that is the same effect as a diffraction grating spectroscope as seen below.

Opal can also occur in cavities in the rock where the water can congregate and dry slowly, allowing the silicon to form the opal. Examples can be seen in these Koroit Opals from Australia.

Specimens from the ISG Student Reference Collection. Courtesy of Gene McDevitt, McDevitt Opal Mining. koroit.com

Qualities

Opals occur in so many varieties and colors that it is difficult to find all of the possibilities in a book, much less a newsletter. From the Ethiopian Welo opal seen here, to the Australian opal seen above, to the Mexican Fire Opal seen below.

You should note that the term fire opal does not mean an opal with a lot of fire. It is a specific name for a variety of opal that is translucent to semi-transparent, yellow to orange in color, and is normally faceted…although can be cut en cabochon. I hear many, many jewelers incorrectly refer to nice quality crystal opals as “fire opal”.  Fire opal qualities seen below.

Unusual Properties: Endless.

Every opal is unique, and the color and pattern possibilities are endless. Opals do occur showing asterism and chatoyancy. Here is a photograph of a fern type inclusion in an Ethiopian Welo Opal taken in the ISG Gem Lab.

Study specimen courtesy of opalholicsanonymous.com

Lab Created Opal

It should also be noted that opals, being a simple silicon dioxide, have been created in a lab. The finest by far is the Chatham Created Opal (below left). Easier to identify but also prevalent on the market are Gilson Created Opal (below center) and a created black opal from Russia (below right).

Gemological Properties

Source: Most important deposits in Australia, Brazil, Ethiopia, US (Nevada), and many others possible.
Chemical: SiO2 with H2O
Colors: Endless.
Wearability: Fair. Opals have a hardness that averages 6 on the Mohs Hardness Scale. It makes better necklaces and earrings than rings as far as long-term wear is concerned.
RI: 1.44 – 1.46
Birefringence: None
Optic Character: None
Specific Gravity: 2.10 average but can vary widely based on the amount of water contained in the stone.
Crystal System: Amorphous: no crystal structure
Hardness: 6 average
Transparency: Translucent to Opaque

I hope you enjoyed this fun look of how gemology plays an important part in all phases of a jewelry store operation. If you are interested in the world’s most amazing (and affordable) study of gemology and jewelry appraisal, we invite you to review our program by clicking here.

View additional ISG Education Series articles below:

  • The Story of Ammolite
  • The Story of Aquamarine
  • The Story of Quartz 
  • The Story of Abalone Shell 
  • Where Gemology Meets Horology 
  • The Story of Amber
  • Brazil: Where Gemstones Form
Robert James FGA, GG

Robert James FGA, GG

Robert James, FGA, GG is President of the International School of Gemology, a gemological education organization that offers world class gemology training and boasts the world’s lowest tuition rate. They are innovators in affordable, quality distance education in gemology and jewelry appraisal, based on their certified insurance industry education delivery system. ISG’s online gemology courses are considered tops for quality, affordability and ease of learning.

Related Posts

Image of Chuck Koehler

The Retailer’s Perspective: Just Say No! If You Can

March 31, 2023

The Story Behind the Stone: The Wonder of it All

March 31, 2023
Is the customer always right?

Successful Custom: Stressing the bench jeweler

March 27, 2023

The Story Behind the Stone: Diamonds on Pins and Needles

March 20, 2023

Latest News

Featured

Father’s wisdom takes NM jeweler to fourth generation

March 31, 2023
Featured

75 years Young: Strong women always innovating

March 31, 2023
Featured

An Ocean Full of Diamonds

March 31, 2023

Other News

RDI Diamonds provides business solutions for independent jewelers

The Retailer’s Perspective: Just Say No! If You Can

The Story Behind the Stone: The Wonder of it All

JSA offers recommendations for what to do in a robbery

Ethical Metalsmiths announces launch of Grantorship Program

Jewelers Mutual® Group celebrates 110 years

Southern Jewelry News

© 2022 Southern Jewelry News.

Additional Information

  • About
  • 2023 Jewelry Trade Shows & Events
  • Media Kit
  • Contact
  • Sitemap
  • Newsletter Signup

Get Social with Us

No Result
View All Result
  • Featured Articles
    • Featured
    • Featured Retailers
    • Retailer Roundtable
    • Supplier Spotlight
    • Sponsored Content
  • Latest News
    • What’s New
    • Industry Events
    • Tradeshow News
    • On The Move
    • Other News
    • Furry Friends
  • Podcast
  • Columnists
  • Classifieds
  • Subscriptions
    • Newsletter Signup
    • Print Subscription

© 2022 Southern Jewelry News.