Black Opal Gemstone 15.74ct
This Black Opal is Natural Gemstone Which is Black Multicolour, it’s Originates from Ethiopia and it’s Exact Weight is 15.74ct, The Measurements are 24.83×13.67×8.13mm, The Shape and Cut of This Stone is Oval Cabochon It’s Graded Opaque and Clarity is Good. This 15.74ct Black Multicolour Natural Black Opal Gem is available for Ready to Ship anywhere in The World. You Can also Select Certification and Shipment Method as Optional.
|Species||Natural Black Opal|
Black Opal Gemstone 15.74ct
Properties Of Black Opal Gemstone
Chemical Composition: SiO2 + 5-10% nH2O [Hydrated Silicon Dioxide]
Hardness: 5.5 – 6.0
Specific Gravity (Density): 1.90 – 2.30
Refractive Index: 1.43
About :Black Opal Gemstone
Opal gets its name from Opalus, the ancient Latin name which was probably derived from the Sanskrit word Upala, meaning precious stone. The Greek word opallios literally means to see a change of colour.
Opal comes in a wide variety of types and colours from many locations world wide. Opal has almost as many names as locations. Some Opal names are in reference to their localities such as Lightning Ridge, Coober Pedy and Virgin Valley. Other names are due to their colour or type such as Cherry, Common, Girasol, Hyalite, Water, Fire, Jelly, Milk, Black, Crystal, Hydrophane, Moss and Harlequin. Many Opals are transparent but others are only known to be opaque and are made into beautiful cabochons with amazing colour play like Australian Opals. Australian Opal cabochons can have translucent to opaque white, grey or black body colours with a beautiful colour play on their surface.
Transparent opals may have solid body colours with no colour play or they may be lightly coloured or colourless but show beautiful internal colour play with all the colours of a rainbow. These may be called Contra Luz or Precious Opal because of their amazing internal colour play when lighted from behind. Some Opals from Ethiopia have both strong body colours and beautiful internal colour play. Faceted Brazilian and Mexican Opals are usually found in vivid colours of yellow, orange and red. They are often called Fire Opals for their body colours resembling the colours of fire, not due to internal fire or colour play. Colourless Opals are often called Jelly, Water, Crystal, Girasol or Hyalite Opal. Hyalite Opal from Madagascar is colourless with a soft, beautiful glow. There are also opaque Opals with no colour play just beautiful pastel colours like Pink Opal from Peru; Blue Opal from Owyhee, Oregon; and pale green Opal from Siberia and Africa. The USA has several locations known for beautiful Opals including Idaho, Oregon and Nevada.
Although Opal is amorphous (no crystal structure) it does have a structure of sorts. Opal is composed of tiny spherical particles as a solidified gel also containing 5-10% water. Random chains of silicon dioxide and water are arranged into tiny spheres. In most Opals, these spheres are irregular in size and concentration, kind of jumbled. But in Opals with colour play, such as Contra-luz or Precious Opal, there are many pockets of spheres that are of the approximately equal size and have a regular concentration, or structure. The water contained in these pockets of a somewhat organised structure has the effect of diffracting light at various wavelengths creating a display of different colours. This effect is similar to when a rainbow is created from the sun shining through water particles in the air. Each pocket may produce a different colour or different intensity of colour depending on their angle in the composition and the angle at which the gem is viewed. This effect creates the beautiful colour play or opalescence that makes some Opals much more valuable than others.
Since Opal contains water, it may also dehydrate causing it to craze, crack or become very cloudy or even opaque. This may happen as soon as it is removed from the ground or years later. When this happens, a beautiful Opal may become ugly and worthless.
Of all the Opal taken out of the ground, 95% is valueless pitch and 95% of the remainder is low quality. Only a mere 0.25% ever makes it to market as a gem.