White Opal & Crystal Opal
Coober Pedy white opal and Australian crystal opal varieties - characteristics, quality grades, and market position.
Introduction
Coober Pedy, South Australia, whose name derives from the Aboriginal phrase
"kupa piti" (white man's hole), was first worked for opal in 1915 and is now the
largest opal mining area in the world. [1] Underground
shaft mining dominates because the desert climate makes surface work impractical;
miners historically lived in subterranean "dugout" homes excavated from the
Cretaceous sandstone.
White opal occupies the N7–N9 body-tone range; the pale background limits contrast,
making brightness the critical value factor. Vivid full-spectrum broadflash with red
fire on a white opal rivals some black opal in appeal. Crystal opal, transparent
to semi-transparent, displays play-of-colour with a depth that white opal cannot
match.
Treatment distinction is commercially important: doublets and triplets (thin opal
slices on a backing, with or without a clear cap) are widely sold in fashion
jewellery. Verification that opal is solid rather than composite is essential before
assessing value. [2]
Coober Pedy White Opal
The world's largest opal field:
Source
Characteristics
- Body colour: White to light grey (N7-N9)
- Play-of-colour: All colours possible
- Volume: Vast majority of Australian production
- Quality range: Commercial to fine
White Opal Quality
Quality factors in white opal:
Body Tone
- N7-N9 on body tone scale
- Lighter background than black opal
- Less contrast for play-of-colour
- Some prefer softer aesthetic
Play-of-Colour
- Brightness: Key value determinant
- Coverage: Full face coverage ideal
- Colours: Full spectrum more valuable
- Red presence: Adds significant premium
- Pattern: Similar patterns to black opal
Crystal Opal
Transparent to translucent opal variety:
Characteristics
- Body: Transparent to translucent
- Play-of-colour: Visible through body
- Sources: Lightning Ridge, Coober Pedy, others
- Effect: Depth and dimension to colour display
Black Crystal
- Dark transparent body
- Exceptional light transmission
- Shows play-of-colour with depth
- Premium variety; rare
Light Crystal
- Clear to light grey body
- More common than black crystal
- Beautiful depth effects
- Good value option
Other Australian Opal Sources
Additional white and light opal production:
Andamooka
- South Australian field
- Matrix opal notable
- Some treated (sugar-acid)
- Variable quality
Mintabie
- Northern South Australia
- Quality approaching black opal
- Limited production
- Collector interest
White Cliffs
- Historic NSW deposit
- First major Australian opal field
- Limited current production
- Historic significance
Quality Grading
| Grade | Brightness | Body Tone | Value Range |
|---|---|---|---|
| Gem | Brilliant | N7-N8 | High |
| Fine | Bright | N7-N9 | Medium-High |
| Good | Moderate | N8-N9 | Medium |
| Commercial | Subdued | N9 | Accessible |
Market Position
White and crystal opal in the market:
- Accessibility: Wide price range available
- Volume: Most common Australian opal type
- Fine quality: Can command good prices
- Crystal premium: Good crystal opal valued
- Fashion jewellery: Major market segment
- Treatment note: Some material treated (doublets, triplets)
Doublets and Triplets
References
- ↑ 1. Schumann, W. (2009). Gemstones of the World (4th ed.). Sterling Publishing. ISBN: 978-1-4027-6829-3.
- ↑ 2. Read, P. (2014). Gemmology (3rd ed.). Butterworth-Heinemann. DOI: 10.4324/9780080507224.