Boulder Opal

OPAL

Jelly Opal
Yowah Nut Opal Hyalite Precious Opal Opalite
  Like: Share:  

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 - Hover over an item for more information
Round Blue Topaz Sterling Silver Engagement Ring with Fire Opal - Hurricane Ring
This graceful three-stone ring design with three round brilliant gemstones has curves that embrace the gems in an unusually elegant way.Only $315.00 at Gemvara
no photoRound Blue Topaz Sterling Silver Engagement Ring with Fire Opal - Hurricane Ring
$315.00
Gemvara
2.22 TCW Cubic Zirconia and Lab Created Blue Opal Earrings with Omega Backs in Sterling Silver
. A punch of purple power. Sparkling with rich hues, these earrings include oval-cut purple cubic zirconia stones capturing a luxe-lifestyle look with their ultra-rich design sparked by white cubic zirconia accents. 2.22 carats T.W. Inlaid lab-created...Only $71.24 at PalmBeachJewelry
no photo2.22 TCW Cubic Zirconia and Lab Created Blue Opal Earrings with Omega Backs in Sterling Silver
$71.24
PalmBeachJewelry
Round Red Garnet Sterling Silver Vintage-Inspired Ring with Diamond & Fire Opal - Venus Band
Scalloped shells form a fluted pattern on each side of this feminine tapered band, carefully handcrafted in your choice of gems and metals.Only $220.00 at Gemvara
no photoRound Red Garnet Sterling Silver Vintage-Inspired Ring with Diamond & Fire Opal - Venus Band
$220.00
Gemvara
Round Fire Opal Sterling Silver Vintage-Inspired Ring with Diamond & Red Garnet - Venus Band
Scalloped shells form a fluted pattern on each side of this feminine tapered band, carefully handcrafted in your choice of gems and metals.Only $220.00 at Gemvara
no photoRound Fire Opal Sterling Silver Vintage-Inspired Ring with Diamond & Red Garnet - Venus Band
$220.00
Gemvara
Birthstone Heart Cross - October (Opal)
Superbly crafted with rich 14kt gold-plating, this breathtaking cross is radiant with 12 genuine opals. The shimmering stones are precisely inlaid along the path of the cross, which is surrounded by a gleaming 14kt gold-plated eternity heart. For ideal...Only $99.00 at Danbury Mint
no photoBirthstone Heart Cross - October (Opal)
$99.00
Danbury Mint
Round Alexandrite Sterling Silver Mother's Ring with Peridot & Fire Opal - Liana Ring with Three Gems
This lovely leafy vine ring twines across the finger while brilliant gems bloom among the leaves.Only $230.00 at Gemvara
no photoRound Alexandrite Sterling Silver Mother's Ring with Peridot & Fire Opal - Liana Ring with Three Gems
$230.00
Gemvara
Lab Created Opal & Diamond Accent Bracelet, White, Womens
Glitz and glamor with every twist of your wrist in this lab created opal and diamond accent bracelet. Metal: Sterling silverStone: 7 ctw. lab created white oval opal, 6mmx4mmOther Stones: Diamond accentsSetting: ProngClosure: Lobster claspLength: 7...Only $145.81 at jcpenney
no photoLab Created Opal & Diamond Accent Bracelet, White, Womens
$145.81
jcpenney
Sterling Silver Promise Ring with Sapphire & Fire Opal - Two Hearts Ring
Two hearts meet in one simply perfect ring style. Create this style in your birthstones to add extra meaning.Only $230.00 at Gemvara
no photoSterling Silver Promise Ring with Sapphire & Fire Opal - Two Hearts Ring
$230.00
Gemvara
Princess Black Onyx Sterling Silver Engagement Ring with Black Onyx & Fire Opal - Ianna Ring
A 5mm, princess-cut center stone is enhanced by accent gems set into this gorgeous band, handcrafted in your choice of gems and metals.Only $350.00 at Gemvara
no photoPrincess Black Onyx Sterling Silver Engagement Ring with Black Onyx & Fire Opal - Ianna Ring
$350.00
Gemvara
Emerald-Cut Fire Opal Sterling Silver Vintage-Inspired Engagement Ring with Citrine & Fire Opal - Emerald Isle Ring
This captivating emerald-cut solitaire ring is accented by six pave-set gems along its shoulders. A sculpted braided design begins and ends with pave side accents for vintage appeal.Only $705.00 at Gemvara
no photoEmerald-Cut Fire Opal Sterling Silver Vintage-Inspired Engagement Ring with Citrine & Fire Opal - Emerald Isle Ring
$705.00
Gemvara
Genuine Opal & Diamond-Accent Bracelet In Sterling Silver, White, Womens
Alluring and delicate, this genuine opal and diamond-accent pendant is crafted in brightly polished sterling silver. Metal: Sterling silverStone: Genuine opalOther Stones: Diamond accents Setting: ProngClosure: Lobster claspLength: 7 1/4in Gemstones...Only $124.98 at jcpenney
no photoGenuine Opal & Diamond-Accent Bracelet In Sterling Silver, White, Womens
$124.98
jcpenney
Round Fire Opal Sterling Silver Mother's Ring with Citrine & Ruby - Liana Ring with Three Gems
This lovely leafy vine ring twines across the finger while brilliant gems bloom among the leaves.Only $205.00 at Gemvara
no photoRound Fire Opal Sterling Silver Mother's Ring with Citrine & Ruby - Liana Ring with Three Gems
$205.00
Gemvara
Emerald-Cut Fire Opal Sterling Silver Engagement Ring - Ara Ring
A classic, four-prong setting is the perfect way to display this 6mm showstopper, emerald-cut gem.Only $265.00 at Gemvara
no photoEmerald-Cut Fire Opal Sterling Silver Engagement Ring - Ara Ring
$265.00
Gemvara
Sterling Silver Rainbow Fire Australian Black Opal Doublet (Boulder Opal) Bracelet Jewelry
This Bracelet was handmade by a master artisan and is one of a kind.Only $209.24 at JeGem.com
no photoSterling Silver Rainbow Fire Australian Black Opal Doublet (Boulder Opal) Bracelet Jewelry
$209.24
JeGem.com
Round Sapphire Sterling Silver Promise Ring with Fire Opal & Diamond - Modern Heart Ring
This stylishly-simple heart ring is carefully handcrafted in your choice of gems and metals.Only $265.00 at Gemvara
no photoRound Sapphire Sterling Silver Promise Ring with Fire Opal & Diamond - Modern Heart Ring
$265.00
Gemvara

This Site Awarded
Available OPAL specimens:
see this List of ALL specimens including SOLD ones
 

Copyright ©1995-2013 by Amethyst Galleries, Inc.
Site design & programming by galleries.com web services