OPAL

• Chemistry: SiO₂ - nH₂O; Hydrated Silicon Dioxide.
• Class: Mineraloids
• Group: Some minerologists place Opal in the Quartz Group.
• Uses: As a gemstone and ornamental stone.
• The Physical Properties of Opal
• For natural opal mineral specimens see our For Sale or Sold lists

  For Opal Jewelry, see -->

  OPAL JEWELRY

Although there is no crystal structure, (meaning a regular arrangement of atoms) opal does possess a structure nonetheless. Random chains of silicon and oxygen are packed into extraordinarily tiny spheres. These spheres in most Opals are irregular in size and inconsistent in concentration. Yet in Precious Opal, the variety used most often in jewelry, there are many organized pockets of the spheres. These pockets contain spheres of approximately equal size and have a regular concentration, or structure, of the spheres. This has the effect of diffracting light at various wavelengths, creating colors. Each pocket produces a different color and with a different intensity, depending on the angle from which a viewer sees it. The multicolored flashes of light that Opal emits gives it a truly beautiful and valuable look. This effect is called a "play of light", and not "opalescence". The latter term describes the milky nature of the translucence of opal, and is more properly compared to the appearance of water to which a few drops of milk have been added.

The name opal probably is derived from the Sanskrit name for precious stone; upala. It has been mined for centuries, at least since Roman times when they extracted the opal from areas now within the Czech Republic. The Aztecs made use of local Mexican sources as did the Spaniards when they exported the material back to Europe. Today most precious opal comes from Australia with significant sources from Mexico and the Western United States.

Not all opal is so precious however. Common opal lacks opalescence, color or luster and is . . . after all . . . common. Opal is often imitated, forged and "enhanced". Fluorescence, while somewhat unreliable is a good method to determine authenticity.

Opal is the modern Birthstone for October.

PHYSICAL CHARACTERISTICS:

• Color is white, colorless, pale yellow, pale red, gray or black when impurities are common. Diffraction can cause flashes of any color of the rainbow (play of light).
• Luster is vitreous to pearly.
• Transparency: Specimens are transparent to translucent (opalescent).
• Crystal System: Does not apply because opal is amorphous.
• Habits include massive, cavity-fillings such as in fractures and geodes, nodular, reniform or as a replacement of other minerals and wood.
• Cleavage is absent.
• Fracture is conchoidal.
• Hardness is 5.5 - 6
• Specific Gravity is approximately 2 - 2.5 (light)
• Streak is white.
• Other Characteristics: Most specimens will fluoresce white or pale green, some phosphoresce and all specimens can be very sensitive to impacts and low temperatures.
• Associated rocks are chert (a form of microcrystalline quartz), volcanic rocks and many others.
• Notable Occurrences include many Western USA localities; Mexico; Australia; England; Czech Republic and many other localities around the world.
• Best Field Indicators are color play & opalescence, low density, fluorescence, fracture filling tendency and lack of cleavage or crystal faces.

Amethyst Galleries sells natural opal specimens. For Fine Jewelry, see our affiliates:

Opal Jewelry Powered by Bizrate - Hover over an item for more information

Opal and Diamond Stud Earrings in 18k White Gold (5mm)
Demure and unique, these petite opal and diamond earrings are set in 18k white gold featuring petite round diamonds that complement the fire of colorful opals.Only $340.00 at

Opal and Diamond Stud Earrings in 18k White Gold (5mm)
$340.00

Opal Earrings with Diamonds 2.0 Carat (ctw) in Sterling Silver
FREE Shipping! Opal Earrings with Diamonds 2.0 Carat (ctw) in Sterling Silver #61CK8925COP. These alluring 2.0 carat (ctw) gemstone and diamond earrings boast two lustrous pearls and are crafted from polished white sterling silver. Each earring...Only $99.00 at

Opal Earrings with Diamonds 2.0 Carat (ctw) in Sterling Silver
$99.00

Dot Dash Band, Sterling Silver Ring with Fire Opal & Citrine
This airy band designed by Tony Rodrigues is punctuated by brilliant bezel-set gems all the way around. Pick one gem or alternate two: either way you'll love the look.Only $309.00 at

Dot Dash Band, Sterling Silver Ring with Fire Opal & Citrine
$309.00

Ross-Simons Opal and 8.90 ct. t.w. Topaz Earrings In Sterling Silver
Update your look with a sea of color with these vibrant opal and 8.90 ct. t.w. topaz earrings. Finely crafted with blue and green swirled opals and blue topaz squares. Clutch/post, sterling silver earrings. Opal birthstones are the perfect gift for...Only $187.50 at

Ross-Simons Opal and 8.90 ct. t.w. Topaz Earrings In Sterling Silver
$187.50

Round Solitaire Stack Ring, 14K Yellow Gold Ring with Fire Opal
This delicate round brilliant solitaire ring by designer Ji Hwang is lovely alone but is designed to be perfect to stack with other rings.Only $523.00 at

Round Solitaire Stack Ring, 14K Yellow Gold Ring with Fire Opal
$523.00

Claddagh Ring, Heart Fire Opal Sterling Silver Ring with Citrine & Blue Topaz
This timeless design by Jessica Bezhad is inspired by the traditional Irish Claddagh Ring, which is given as a token of love or of marriage. The heart symbolizes love, the hands friendship and the crown, loyalty.Only $444.00 at

Claddagh Ring, Heart Fire Opal Sterling Silver Ring with Citrine & Blue Topaz
$444.00

Boulevard Ring, Oval Fire Opal Sterling Silver Ring with Ruby
The curves of a brilliant oval center gem are enhanced by the pure lines of the gem-paved band.Only $540.00 at

Boulevard Ring, Oval Fire Opal Sterling Silver Ring with Ruby
$540.00

Birds of a Feather Ring, Round Fire Opal Sterling Silver Ring
This lovely sensuous feather ring designed by Ji Hwang can be worn with the gem in front or in back, desending on your mood.Only $302.00 at

Birds of a Feather Ring, Round Fire Opal Sterling Silver Ring
$302.00

Daisy Ring, 14K Rose Gold Ring with Fire Opal
This nature-inspired ring by designer Ji Hwang is the perfect everyday choice with a pretty petite gem-set bloom on a delicate modern band. Wear more than one to create a bouquet for your finger.Only $571.00 at

Daisy Ring, 14K Rose Gold Ring with Fire Opal
$571.00

Solo Ring, Oval Fire Opal Sterling Silver Ring
This sleek ring with an oval gemstone is lovely worn alone but also stacks beautifully. Wear several in different metals or different gems for a sophisticated look.Only $315.00 at

Solo Ring, Oval Fire Opal Sterling Silver Ring
$315.00

Spark My Heart Pendant, Heart Aquamarine 14K Yellow Gold Necklace with Fire Opal
The classic solitaire pendant is updated with a romantic heart-shaped gemstone and an accent gemstone adds extra brilliance.Only $631.00 at

Spark My Heart Pendant, Heart Aquamarine 14K Yellow Gold Necklace with Fire Opal
$631.00

Alexis Bittar Hinged Multi-Stone Bracelet
Ruthenium plate shapes pronged silhouette. Geometric-cut white quartz ends with opal foil underlayer. Multicolor pave Swarovski&#174 crystals. Hinged magnetic closure. Approximately 2 1/2"W. Made in USA. Keywords: April,Birthstone,bracelet,diamond...Only $450.00 at

Alexis Bittar Hinged Multi-Stone Bracelet
$450.00

JeGem Sterling Silver Rainbow Fire Solid Australian Crystal Opal Ring
This Ring was handmade by a master artisan and is one-of-a-kind.Only $70.06 at

JeGem Sterling Silver Rainbow Fire Solid Australian Crystal Opal Ring
$70.06

Wisteria Pendant, Pear Fire Opal Sterling Silver Necklace with Citrine & White Sapphire
Graceful curves, arcing leaves and a sinuous form come together in this beautiful necklace design by Jessica Behzad.Only $324.00 at

Wisteria Pendant, Pear Fire Opal Sterling Silver Necklace with Citrine & White Sapphire
$324.00

Created Blue Opal Earring and Pendant Set 1/2 Carat (ctw) in Sterling Silver with Chain
Created Blue Opal Earring and Pendant Set 1/2 Carat (ctw) in Sterling Silver with Chain #61QG0205COP. This refreshingly bright 1/2 carat (ctw) gemstone earring and pendant set boasts three round brilliant cut blue opal stones is crafted from sleek...Only $69.95 at

Created Blue Opal Earring and Pendant Set 1/2 Carat (ctw) in Sterling Silver with Chain
$69.95

See More Opal Jewelry Selections at Bizrate

Groupings

Birthstones

By Name Framed
Unframed

By Class Carbonates
Elements
Halides
Oxides
Phosphates
Silicates
Sulfates
Sulfides

Fluorescent Minerals

Properties

Rocks

Search

View Cart

Books