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About Black Opal – History and Introduction

Black opal is one of the many fascinating varieties of opal available today and it also happens to be one of the most popular varieties. In 2008, Australia officially recognized this and proclaimed black opal to be the official state gemstone for New South Wales. Common opal was already the official gemstone representing all of Australia, because, amazingly, almost all of the world's supply of black opal is mined from New South Wales and an astonishing 97% of all common opal is sourced from Australia.


Black opal is by far the most valuable and appreciated of all opal varieties, especially those from Australia's famous Lightning Ridge. Often, black opal stones will contain aspects of common opal which remain intact throughout production. Typically, common opal is strategically left on the backside of finished black opal stones. The common opal, referred to as 'potch', actually enhances the black opal body tone and accentuates the boisterous vibrancy of other colours that black opal can radiate. It is because of black opal's ability to display such vivid and intense colors that black opal is considered to be the most valuable type of opal available today.


Black opal body tones range from a dark gray to black, and the dark background acts as the base for the spectrum of colors it can display. Despite its descriptive name, black opal can, in fact, encompass various colours. Top quality specimens can reflect the full spectrum of colours through their unique play of colour quality.


Black opals can easily be distinguished from common opals by the colour of their body tone. However, identifying natural untreated black opal from synthetic, lab created or treated opal can be nearly impossible without proper lab testing and equipment. Typically, if the black opal appears to be too colourful and too perfectly patterned, there is a good chance that it has been enhanced. Natural untreated black opal will typically always have flaws, which make the stone unique.


Black Opal Origin and Gemstone Sources Go back to the Top

Almost all black opals are mined from Northern New South Wales and the majority of these are mined specifically from Lightning Ridge. Lighting Ridge has become known as the world's biggest supplier of black opal, and extracts incredible amounts of opal all year round. Other sources for black opal include Ethiopia, but Ethiopian black opal is usually enhanced through smoke treatment to darken the body tone colour. No other origin or source can rival the quality and colour of Australia's black opal.


Buying Black Opal and Determining Black Opal Gemstone Value Go back to the Top

Black Opal Colour


Black opal contains subtle traces of iron oxide and carbon elements, which are not found in common opal. These combined elements are responsible for creating the unique traits belonging to black opal. The dark canvas of black opal results in the distinction and reflection of much brighter colours compared to other varieties of opal. Yellow, blue and green are the most common colours seen through play of colour, whereas violet, fiery red and orange colours are the most valuable and sought after of opal colours.


Black Opal Clarity and Luster


Black opal clarity is typically translucent to opaque and almost all specimens will have eye visible inclusions such as patches or lines of potch (common opal). With black opal, it is the presence of crazing that can render a specimen worthless. Crazing is due to the drying of opal and it results in surface-reaching cracks or fissures. Black opal should have a wax-like luster, but at the same time, it should not appear to be too 'plasticky'.


Black Opal Cut and Shape


Typically, the shape and cut of a finished black opal will be dependent on the original opal rough. Black opals are most often cut into oval cabochons, but other shapes are also very popular, such as teardrops and trillion shapes. Most black opals are cut with low domes because they have rather thin colour bars. If the opal colour bar is too thin, it may be unfeasible to fashion any domed surface at all from the stone.


Black Opal Treatment


Ethiopia is a major source for treated black opal. The treatment used on Ethiopian opal is an old smoking method which allows carbon to deeply penetrate the opal and enhance its color. There have been recently reported enhancements involving a combination of heat and sugar; stones are soaked in a sugar solution and then dipped in sulfuric acid. They are then slowly heated to produce a darker body tone.


Another treatment that has been discovered on some black opal is coating of the gem. This is not as common as heating, but nevertheless, consumers should be aware of this possible enhancement, along with the possibility of impregnation with polymer, resin or oil that is done to stabilize opal.

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Black Opal

About Black Opal - History and Introduction

Historical values 2005 - 2016 Not Available

Spectrum

Spectrum Description; Occurrence

1 ct.

3 ct.

5 ct.

10 ct.

30 ct.

X1 - Extra Wide Intense.

Strong radiance and exceptional color play in a wide spectral range. Splashes fill over 90% of the body. Rich, contrast pattern. Origin: Ethiopia.

Alternative name, occurrence category: Common

454.78

526.08

597.38

775.63

1,488.61

X1-RO - Red-Orange shift.

Strong radiance, intense color play with a dominance of red, orange and yellow hues. Splashes fill over 90% of the body. Origin: Ethiopia.

Alternative name, occurrence category: Common

404.01

467.34

530.68

689.03

1,322.40

X1-GG - Green-Gold shift.

Strong radiance, intense color play with a dominance of green and warm yellow hues. Splashes fill over 90% of the body. Origin: Ethiopia.

Alternative name, occurrence category: Common

358.13

414.27

470.42

610.78

1,172.23

X1-GB - Green-Blue shift.

Strong radiance, intense color play with a dominance of green, blue and violet hues. Splashes fill over 90% of the body. Origin: Ethiopia.

Alternative name, occurrence category: Common

330.51

382.33

434.14

563.68

1,081.83

X2 - Wide Intense.

Good radiance and wide color play with a single hue prevailed. Splashes fill over 70% of the body. Sharp, distinct pattern. Origin: Ethiopia.

Alternative name, occurrence category: Common

280.18

324.10

368.02

477.84

917.08

X3 - Evident.

Moderate radiance and reduced color play. Splashes fill over 50% of the body. Origin: Ethiopia.

Alternative name, occurrence category: Common

216.03

249.90

283.77

368.44

707.13

G1 - Vivid Grain.

Strong radiance and color play. Splashes fill over 70% of the body. Sharp granular or pinpoint pattern. Origin: Ethiopia.

Alternative name, occurrence category: Common

259.24

299.88

340.53

442.13

848.55

G2 - Dim Grain.

Moderate radiance and reduced color play. Splashes fill over 50% of the body. Origin: Ethiopia.

Alternative name, occurrence category: Common

201.33

232.90

264.46

343.37

659.01

PP - Poor.

Poor radiance with scanty color play. Origin: Ethiopia.

Alternative name, occurrence category: Common

136.30

157.67

179.04

232.46

446.15

TOP

Opal (Ethiopia)

Colour: wide spectrum of multicolor splashes with the body tones from colorless/milky to deep black.

Hardness: 5.5 - 6.5

Refractive index: 1.42 - 1.47

Density: 1.95 - 2.35

Chemical composition: SIO2*nH2O

Crystal structure: amorphous

Origins: Australia (the major source), Ethiopia, Mexico, Honduras, Guatemala, Brazil, USA, Canada, Madagascar, Tanzania, Czech, Slovakia.

An opal is an amorphous form of silica (in the quartz group of minerals). Precious opals from Australia or Ethiopia have an intense colour play in a wide spectral range. Opals contain layers of microspheres of silica, which produce the effect of light interference. The Colour grading system for opals is based on two scales: Spectrum & Body Tone. Black opals with intense red colour splashes are considered the most valuable gemstones. Opals are not treated.