Gemstone profile and identification guide
A dark body tone turns black opal into a stage for moving colour. Against that deeper background, flashes of red, green, blue, and orange can appear sharper and more dramatic than they do in lighter opal varieties.
A dark body tone turns black opal into a stage for moving colour. Against that deeper background, flashes of red, green, blue, and orange can appear sharper and more dramatic than they do in lighter opal varieties.
Did you know? Black opal from Lightning Ridge in Australia set the benchmark for this variety and remains one of the best-known sources in the trade.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Name: Black Opal
Scientific classification: Mineraloid (Opal)
Hardness: 5.5 Mohs
Transparency: opaque to translucent
Lustre: vitreous to waxy
Crystal system: Amorphous
Primary colour: Black
Secondary colour: Not specified
Colour family: Neutrals
Separate it from dyed imitations by studying whether the play of colour moves naturally through the stone rather than sitting in fixed patches. The dark background should support the flashes, not smother them.
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity fields reviewed against consensus gemological references (GIA/Gem-A/Mindat/IGS).
Some market- and locality-level details may still require citation-grade source notes for publication workflows.
Hardness category: soft
Hardness value: 5.5 Mohs
Chemical composition: Hydrated silica (SiO2.nH2O)
Crystal system: Amorphous
Common locations: Australia (Lightning Ridge, primary commercial source); Ethiopia (Wollo) and minor occurrences elsewhere
Learn more: Gem-A gemstone education resources.
Black Opal is listed in the neutrals grouping, with black as the dominant body colour. Some specimens also show opalescence, play of colour, iridescence, which can alter the way the colour is perceived under changing light.
Optical effects: Play of Colour
Mineral species: Opal
Mineral group: Opal mineraloid
Chemical formula: Hydrated silica (SiO2.nH2O)
Mohs hardness: 5.5
Crystal system: Amorphous
Lustre: vitreous to waxy
Transparency: opaque to translucent
Streak: White
Cleavage: None
Fracture: Conchoidal to uneven
Specific gravity: 1.98-2.25
Refractive index: 1.37-1.52 (typically ~1.44-1.46)
Optical phenomena: Play of Colour
Colour range: Black, Multicolour
Common inclusions: Potch layers, ironstone matrix, crazing (fracture networks)
Geological environment: Black Opal occurs in Low-temperature silica deposition in sedimentary host rocks. Its Amorphous structure reflects the pressure-temperature conditions of those host rocks, with notable occurrences in Australia (Lightning Ridge, primary commercial source); Ethiopia (Wollo) and minor occurrences elsewhere.
Principal mining regions: Australia (Lightning Ridge, primary commercial source); Ethiopia (Wollo) and minor occurrences elsewhere
Important commercial sources: Lightning Ridge, New South Wales, Australia is the principal commercial source of black opal
Historical significance: Lightning Ridge black opal is the benchmark material in the modern opal trade.
Common treatments: Sugar-acid or smoke treatment, polymer impregnation, doublet/triplet assembly
Synthetic or imitation forms: Synthetic opal, assembled stones (doublets/triplets), glass imitations
Common look-alikes: Black glass, dyed chalcedony, assembled opal composites
Jewellery uses: Black Opal is used chiefly for Often best in pendants, earrings, collector cuts, and occasional-wear rings that showcase colour without unnecessary risk.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 5.5 guiding suitable jewellery applications.
Care recommendations: Black Opal should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 5.5 in the Amorphous system, avoid steam cleaners, harsh chemicals, and high-impact wear. Store separately from harder gems to minimise abrasion and edge wear.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Black Opal.
Black Opal is a Opal material with chemistry Hydrated silica (SiO2.nH2O). It develops in Low-temperature silica deposition in sedimentary host rocks, and economically significant production is associated with Australia (Lightning Ridge, primary commercial source); Ethiopia (Wollo) and minor occurrences elsewhere.
Lightning Ridge, New South Wales, Australia is the principal commercial source of black opal
Best for: Black Opal is used chiefly for Often best in pendants, earrings, collector cuts, and occasional-wear rings that showcase colour without unnecessary risk.. In the trade it is commonly fashioned as faceted stones, calibrated cuts, and higher-clarity collector pieces, with Mohs hardness 5.5 guiding suitable jewellery applications.
Ideal uses: Often best in pendants, earrings, collector cuts, and occasional-wear rings that showcase colour without unnecessary risk.
Black Opal should be cleaned with lukewarm water, mild soap, and a soft brush. At Mohs 5.5 in the Amorphous system, avoid steam cleaners, harsh chemicals, and high-impact wear. Store separately from harder gems to minimise abrasion and edge wear.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Compare hardness (5.5 Mohs), crystal system (Amorphous), colour profile, and lustre (vitreous to waxy) with your sample. Then cross-check related gemstones listed above.
Black Opal is listed in the neutrals grouping, with black as the dominant body colour. Some specimens also show opalescence, play of colour, iridescence, which can alter the way the colour is perceived under changing light.
Often best in pendants, earrings, collector cuts, and occasional-wear rings that showcase colour without unnecessary risk.. For maintenance, follow the care guidance in this profile.
GIA: general gemstone identity (reviewed) - Reviewed as a direct core gemstone profile.
Gem-A: gemological education and terminology (reviewed) - Reviewed as a direct core gemstone profile.
Mindat: mineral species and locality index (reviewed) - Reviewed as a direct core gemstone profile.
International Gem Society: collector-facing gem reference (reviewed) - Reviewed as a direct core gemstone profile.
