Labradorescence
Labradorescence in labradorite and spectrolite including cause, colour range, quality factors, and distinction from adularescence.
By Fabian Moor
Last updated
phenomena/labradorescence labradorite spectrolite species/feldspar
Introduction
Labradorescence is the striking play of colours seen in labradorite feldspar.
Unlike the soft single-colour glow of adularescence, labradorescence displays
a full spectrum of colours including blue, green, gold, orange, and purple
in distinct flashes.
First identified in specimens from Labrador, Canada in 1770, [1]
this phenomenon creates some of the most visually dramatic effects in the gem world.
Mechanism
The cause of labradorescence:
Lamellar Twinning
- Caused by light interference from repeated thin twin layers
- Twin lamellae form during cooling of plagioclase
- Lamellae vary in thickness, producing different colours
- Light interferes between twin boundaries [2]
Orientation Dependence
- Most prominent on specific crystal planes (001 cleavage)
- Requires proper cutting orientation to display effect
- Colours appear in patches or broad flashes
- Tilting the stone reveals different colour areas
Colour Range
Labradorescence can display nearly the full spectrum:
- Blue: Most common colour seen
- Green: Often with blue
- Gold/yellow: Warm tones
- Orange: Vivid examples exist
- Red: Rarer; highly prized
- Purple: Less common
Multiple colours in one stone are typical and valued.
Spectrolite
Quality Factors
| Factor | Premium Quality |
|---|---|
| Colour range | Multiple vivid colours (spectrolite type) |
| Intensity | Bright, strong flashes |
| Coverage | Large percentage of surface shows effect |
| Flash size | Large, distinct colour areas |
| Body darkness | Darker body enhances colours |
Sources
| Origin | Characteristics |
|---|---|
| Finland | Spectrolite; full colour range |
| Labrador (Canada) | Type locality; blue-green common |
| Madagascar | Good labradorescence; various colours |
| Russia | Quality material available |
| Ukraine | Some production |
Labradorescence vs Adularescence
Labradorescence
- Multiple spectral colours
- Sharp, distinct flashes
- Colours appear in patches
- Caused by lamellar twinning
- Plagioclase (labradorite)
- Effect at surface level
Adularescence
- Single colour (blue or white)
- Soft, floating glow
- Even, billowy appearance
- Caused by layer exsolution
- Alkali feldspar (orthoclase)
- Appears below surface
Cutting Considerations
Proper cutting maximises labradorescence:
Orientation
- Cut to display colours face-up
- Align with cleavage plane for best effect
- May sacrifice weight for optimal display
- Flat backs common to maximise colour area
Cut Styles
- Cabochons: Traditional; shows colours well
- Flat slabs: Maximises colour display area
- Faceted: Possible but reduces phenomenon visibility
- Carvings: Popular for decorative pieces
Market and Value
Labradorite market considerations:
- Spectrolite: Highest prices for fine Finnish material
- Collector stones: Fine multi-colour specimens valued
- Decorative use: Popular for tiles, countertops
- Jewellery: Growing popularity for unique pieces
- Size: Large pieces available (unlike many gems)
References
- ↑ 1. Schumann, W. (2009). Gemstones of the World (4th ed.). Sterling. ISBN: 978-1-4027-6829-3.
- ↑ 2. Miura, Y.; Tomisaka, T.; Kato, A. (1975). Labradorescence and the ideal behavior of thicknesses of alternate lamellae in the Bøggild intergrowth. Mineralogical Journal, 7(6), 526–541. DOI: 10.2465/minerj1953.7.526.