Labradorescence
Labradorescence in labradorite and spectrolite including cause, colour range, quality factors, and distinction from adularescence.
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, 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
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)