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Oregon Opal

 

Opal: USA - Idaho, Nevada, Oregon and other US locations

Prehistoric Discovery; IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

SiO2 + 5-10% nH2O

 

Silicon Dioxide + 5-10% H2O

Molecular Weight:

87.11 gm

Composition:

Silicon

32.24 %

Si

68.98 %

SiO2

 

Hydrogen

3.47 %

H

31.02 %

H2O

 

Oxygen

64.29 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.01-80

Nickel-Strunz 10th Ed. ID:

4.DA.10

 

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
A : With small cations: Silica family

Related to:

n/a

Varieties:

None

Synonyms:

Idaho Opal, Nevada Opal, Oregon Opal, Virgin Valley Opal, and other specific location names

 

 

Crystal Data

   

   

Crystallography:

Amorphous  (no crystalline forms)

Crystal Habit:

Amorphous - (no crystalline forms) Habits include Massive; Concretions; Botryoidal; Stalactitic; Reniform - "kidney like" in shape (e.g. Hematite); cavity fillings (e.g. in fractures and geodes); replacement of other minerals or wood.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

None (amorphous)

Fracture:

Irregular/Uneven, Splintery, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

1.90 - 2.30 (g/cm3)

Luminescence:

Fluorescent; greenish yellow under SW UV, white under LW UV

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Colorless, white, yellow, orange, red, yellowish brown, greenish, blue, gray, black, violet; rare specimens display a play of color

Transparency:

Transparent to Translucent to Opaque

Luster:

Vitreous, Waxy, Pearly, Dull

Refractive Index:

1.43 Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

Weak

Pleochroism:

Distinct; red, orange, yellow, green, blue

 

 

Occurances

   

   

Geological Setting:

Sedimentary and secondary from the alteration of high silica igneous extrusive rocks. Altering volcanic tuffs, basalts.

Common Associations:

n/a

Common Impurities:

None

Type Locality:

n/a

Year Discovered:

Prehistoric discovery

View mineral photos:

Opal Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 

This page contains Opal gems from the USA; Idaho, Nevada, Oregon and other locations. For more general information on Opals and Opals from other locations around the world, please visit our main Opal page.

USA Opal gems for sale:

OPALOR-001

Gem:

Opal - Oregon

Stock #:

OPAL-US-001-OR

Weight:

23.52 ct

Size:

21.82 x 15.34 mm

Shape:

Fancy - Yin Yang

Color:

Bright Orange

Clarity:

Eye Clean

Origin:

Juniper Ridge, Lake County, Oregon, USA

Treatment:

None (natural)

Price:

$650.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

OPALOR-001

A truly unique and spectacular gem! This beautiful gem is from Oregon, USA. It was precision faceted with highest meetpoint accuracy in Munich, Germany. This is a unique and original Yin-Yang design with top color for the location.

 

OpalOR-002

Gem:

Opal - Oregon

Stock #:

OPAL-US-002-OR

Weight:

2.372 ct

Size:

9.84 x 9.84 x 6.54 mm

Shape:

Trillion

Color:

Light blue

Clarity:

Translucent

Origin:

Owyhee State Park, Oregon, USA

Treatment:

None (natural)

Price:

$69.00

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

OpalOR-002

A beautiful Opal from near the Lake Owyhee State Park, Malheur County, Oregon, USA. This type of Opal was discovered in 2003 in an Opal rich area of Oregon.

 

OpalID-003

Gem:

Opal - Idaho

Stock #:

OPAL-US-003-ID

Weight:

1.174 ct

Size:

7.22 x 7.30 x 5.25 mm

Shape:

Twisted Triangle

Color:

Vivid Lemon Yellow

Clarity:

Eye Clean

Origin:

Custer County, Idaho, USA

Treatment:

None (natural)

Price:

$140.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

OpalID-003

Wow! The color of this beautiful Idaho Opal is vivid lemon yellow. It is from Custer County, Idaho, USA. This gem was precision faceted in the US in a cut-corner twisted triangle cut. The triangle shaped table is twisted, or rotated slightly to the right to add interest and make this a truly unique, beautiful and well cut gem.

 

 

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