Boulder Opal

OPAL

 		Jelly Opal
Yowah Nut Opal Hyalite Precious Opal Opalite
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Opal has been a popular gem for many centuries and has a very interesting structure. Opal is considered a mineraloid because this structure is not truly crystalline. The chemistry of Opal is primarily SiO2 and varying amounts of water. The amount of water varies from 5% to 10% and sometimes greater. This water can help geologists determine the temperature of the host rock at the time the opal formed.

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
Open Leaf Necklace, Sterling Silver Necklace with Fire Opal & White Sapphire
Three gems, like drops of glistening dew, adorn this organic leaf pendant design by Ji Hwang.Only $260.00 at Gemvara
no photoOpen Leaf Necklace, Sterling Silver Necklace with Fire Opal & White Sapphire
$260.00
Gemvara
Slim Band, Sterling Silver Ring with Diamond & Fire Opal
This sleek stackable band has ten gems channel set for a slim profile that makes it extremely comfortable to wear.Only $363.00 at Gemvara
no photoSlim Band, Sterling Silver Ring with Diamond & Fire Opal
$363.00
Gemvara
Seed & Pod Eternity Band, Palladium Ring with Fire Opal & Red Garnet
This elegant design by Bijoux & Bijoux has sleek bezel set gems all the way around the finger, with seedlike spheres between each one. Each gem has a sculpted round profile that makes this eternity band beautiful from every angle.Only $597.00 at Gemvara
no photoSeed & Pod Eternity Band, Palladium Ring with Fire Opal & Red Garnet
$597.00
Gemvara
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 MyJewelryBox.com
no photoCreated Blue Opal Earring and Pendant Set 1/2 Carat (ctw) in Sterling Silver with Chain
$69.95
MyJewelryBox.com
Oval Stud Earrings, Oval Fire Opal Sterling Silver Stud Earrings
Simply perfect, these oval-shaped stud earrings are the perfect wear-with-everything accent you'll never take off.Only $260.00 at Gemvara
no photoOval Stud Earrings, Oval Fire Opal Sterling Silver Stud Earrings
$260.00
Gemvara
Evening Stars Band, Sterling Silver Ring with Fire Opal
Brilliant bright gems sparkle in this wide band like the first stars that appear in evening's twilight.Only $357.00 at Gemvara
no photoEvening Stars Band, Sterling Silver Ring with Fire Opal
$357.00
Gemvara
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 MyJewelryBox.com
no photoOpal Earrings with Diamonds 2.0 Carat (ctw) in Sterling Silver
$99.00
MyJewelryBox.com
Quad Gem Culvert Ring, Sterling Silver Ring with Fire Opal
Designer Randy Dixon takes a classic band concept and carves a unique niche for it in a recessed elongated octagon-shape ring top flush-set with four small round gems. Contemporary and stylish, the ring is sentimental, too, able to recognize special...Only $333.00 at Gemvara
no photoQuad Gem Culvert Ring, Sterling Silver Ring with Fire Opal
$333.00
Gemvara
Celtic Sun Ring, Round Fire Opal Sterling Silver Ring
This brilliant ring design by Paul Bierker features the triqueta, the Celtic symbol for the trinity, on each side of a brilliant gemstone.Only $466.00 at Gemvara
no photoCeltic Sun Ring, Round Fire Opal Sterling Silver Ring
$466.00
Gemvara
Sailor's Knot Ring, Round Fire Opal Palladium Ring
The sailor's knot, tied at sea and given to a loved one upon return, is a symbol for the perfect love of two people, with no beginning and no end. The sailor's knots in this design surround a brilliant gem.Only $529.00 at Gemvara
no photoSailor's Knot Ring, Round Fire Opal Palladium Ring
$529.00
Gemvara
Australian Opal Ring with Blue Topaz
Metal: Silver .925Size: All sizes are available. If not we resize them for free of charge.Metal Finish: RhodiumStone/s: Australian Opal + Blue Topaz + CZ This item usually arrives in 2-3 business days. Arrival date depends on the item selected.Shipping...Only $215.54 at Silver Best Buy
no photoAustralian Opal Ring with Blue Topaz
$215.54
Silver Best Buy
Aunt Star's Ring, Oval Fire Opal Sterling Silver Ring with White Sapphire
Like the frothy skirts of Degas' dancers, the center gem of this ballerina-style ring is enhanced by a brilliant skirt of surrounding gems. This ring was named by Sue who customized this ring to match a lost ring that her Aunt Star gave her mother when...Only $542.00 at Gemvara
no photoAunt Star's Ring, Oval Fire Opal Sterling Silver Ring with White Sapphire
$542.00
Gemvara
Alyssa Ring, Pear Fire Opal 14K White Gold Ring with Diamond
Like one perfect tear of joy, a pear-shaped gemstone shines in this classic design. Two side gems add brilliance.Only $538.00 at Gemvara
no photoAlyssa Ring, Pear Fire Opal 14K White Gold Ring with Diamond
$538.00
Gemvara
Double Alexandrite and White Opal Silver Bangle
Metal: Silver .925Size: approx 7"" ( 18 cm ) can also be made for wider wrist.\nMetal Finish: RhodiumStone/s: White Australian Opal 8 pz + Alexandrite 2 pz This item usually arrives in 2-3 business days. Arrival date depends on the item...Only $504.14 at Silver Best Buy
no photoDouble Alexandrite and White Opal Silver Bangle
$504.14
Silver Best Buy
Corsage Ring, Sterling Silver Ring with Black Diamond & Fire Opal
This romantic ring by Shristi Design Group is like a corsage that never fades.Only $306.00 at Gemvara
no photoCorsage Ring, Sterling Silver Ring with Black Diamond & Fire Opal
$306.00
Gemvara
See More Opal Jewelry Selections at Bizrate

This Site Awarded
Available OPAL specimens:
OPAL specimen OPA-51
$ 35.00
Dims: 1.14x0.80x0.55in (2.90x2.04x1.40cm) .... Wt: 0.260oz (7.40g) .... Loc: Lightning Ridge, Australia
The opal on the tip[ of this specimen is intensely green and blue.
no photo
OPA-51
$ 35.00
no photo
OPAL specimen OPA-52
$ 32.00
Dims: 1.16x0.82x0.21in (2.93x2.08x0.54cm) .... Wt: 0.120oz (3.50g) .... Loc: Lightning Ridge, Australia
One side of this opal specimen displays a good play of light in multiple colors, especially red.
no photo
OPA-52
$ 32.00
no photo
see this List of ALL specimens including SOLD ones
 
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