Opal

Q: What is Opal?

Opala é uma forma amorfa de sílica hidratada famosa pelo seu fenómeno único de jogo de cores, chamado opalescência. Este efeito produz flashes de todo o espectro de cores através da difracção de luz em esferas microscópicas de sílica. A Austrália fornece cerca de 95% da produção mundial de opala pre

Q: What is the hardness of Opal?

Opal has a Mohs hardness of 5.0 to 6.5, making it moderate for use in jewelry.

Q: Where is Opal found?

Opal is found in Lightning Ridge (Australia).

Q: How much does Opal cost?

Opal falls into the Budget (< $50/ct) price range. Prices vary based on color, clarity, cut, and origin.

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A hydrated amorphous silica, opal is celebrated for play-of-color, a shifting spectral display of red, green, blue, and gold produced as light diffracts through ordered arrays of microscopic silica spheres. Australia yields roughly ninety percent of the world's precious opal, including white opal from Coober Pedy, black opal from Lightning Ridge, and boulder opal from Queensland, with further sources in Ethiopia and Mexico. Lacking crystalline structure, it measures 5.0 to 6.5 on the Mohs scale. Revered since antiquity and the birthstone for October, opal is classed as semi-precious in the budget tier, yet fine black opal with red fire ranks among the most valuable colored stones per carat.

Physical & Optical Properties

Category Semi-Precious Gems

Mohs Hardness 5,0 – 6,5

Specific Gravity 1,98 – 2,25

Refractive Index 1,37 – 1,52

Crystal System Amorphous

Cleavage None

Fracture Conchoidal,Splintery

Color white

Pleochroism Absent

Mohs Hardness

Mohs hardness of Opal shown against the ten reference minerals, from talc (1) to diamond (10).

Mohs	Reference mineral	Opal
1	Talc
2	Gypsum
3	Calcite
4	Fluorite
5	Apatite	●
6	Orthoclase	●
7	Quartz
8	Topaz
9	Corundum
10	Diamond

Crystal System

Value & Market

Price Tier Budget (< $50/ct)

Where to Buy Opal

Blue Nile Fine jewelry retailer

James Allen Gemstone jewelry

Brilliant Earth Ethically sourced gems

Amazon Wide selection

Links may earn a commission at no extra cost to you.

Cultural Significance

Birthstone Month 10 (modern)

About Opal

Opala é uma forma amorfa de sílica hidratada famosa pelo seu fenómeno único de jogo de cores, chamado opalescência. Este efeito produz flashes de todo o espectro de cores através da difracção de luz em esferas microscópicas de sílica. A Austrália fornece cerca de 95% da produção mundial de opala preciosa, com Lightning Ridge famosa pelas opalas negras preciosas. As opalas de fogo do México exibem cores laranja e vermelha brilhantes. Considerada a pedra de outubro, a opala simboliza criatividade e esperança. Cada opala é única, tornando impossível encontrar duas pedras idênticas.