Pyroxene Group
Pyroxene group gems including jadeite, spodumene (kunzite, hiddenite), and diopside (chrome diopside) with properties and identification.
jadeite kunzite hiddenite diopside jade
Introduction
Jadeite
Jadeite (NaAlSi₂O₆) is the more valuable of the two jade minerals,
prized especially in Asian cultures.
Properties
| Property | Value |
|---|---|
| Crystal system | Monoclinic |
| Hardness | 6.5-7 Mohs |
| Specific gravity | 3.30-3.38 |
| Refractive index | 1.654-1.667 (spot) |
| Character | Aggregate (no single crystal) |
| Toughness | Exceptional (interlocking crystals) |
Colour Varieties
| Colour | Cause | Trade Name |
|---|---|---|
| Imperial green | Chromium | Imperial jade (most valuable) |
| Lavender | Manganese + iron | Lavender jade |
| White | Pure composition | Mutton fat jade |
| Yellow to orange | Iron staining | Yellow jade |
| Black | Iron inclusions | Black jade |
Imperial Jade
The finest jadeite variety:
- Colour: Vivid, saturated green
- Transparency: Semi-transparent
- Texture: Fine-grained, even
- Source: Myanmar (Burma) primarily
- Value: Can exceed fine emerald prices
Major Sources
- Myanmar: Premier source; Imperial green
- Guatemala: Historic; Mesoamerican significance
- Japan: Small deposits
- Russia: Limited production
Imperial Jade Value
Jadeite Identification
Distinguishing jadeite from nephrite and simulants:
Jadeite vs Nephrite
| Property | Jadeite | Nephrite |
|---|---|---|
| Specific gravity | 3.30-3.38 | 2.90-3.02 |
| Refractive index | 1.654-1.667 | 1.606-1.632 |
| Lustre | Vitreous to greasy | Greasy to waxy |
| Colours | More vivid greens; lavender | Greens, creams, browns |
| Value | Higher for fine material | Generally lower |
Treatments
Jadeite undergoes various treatments:
- Type A: Natural, untreated (most valuable)
- Type B: Bleached and polymer-impregnated
- Type B+C: Bleached, dyed, and impregnated
- Type C: Dyed (less common alone)
Infrared spectroscopy detects polymer impregnation.
Spodumene
Spodumene (LiAlSi₂O₆) is a lithium aluminium pyroxene with two important
gem varieties.
Properties
| Property | Value |
|---|---|
| Crystal system | Monoclinic |
| Hardness | 6.5-7 Mohs |
| Specific gravity | 3.15-3.20 |
| Refractive index | 1.660-1.676 |
| Birefringence | 0.014-0.016 |
| Cleavage | Perfect in two directions (90°) |
Kunzite
Pink to lilac spodumene:
- Colour cause: Manganese (Mn³⁺)
- Range: Pale pink to intense lilac-pink
- Pleochroism: Strong (pink to colourless)
- Fluorescence: Strong orange-pink; phosphorescence
- Sources: Afghanistan, Brazil, Madagascar, USA
Hiddenite
Green spodumene:
- Colour cause: Chromium (Cr³⁺) for true hiddenite
- Rarity: True Cr-coloured hiddenite is very rare
- Source: North Carolina (type locality); Afghanistan
- Note: Iron-coloured green spodumene is less valuable
Spodumene Challenges
Chrome Diopside
Chromium-coloured diopside offers affordable green colour:
Properties
- Formula: CaMgSi₂O₆
- Colour: Rich green (Cr-coloured)
- RI: 1.675-1.701
- SG: 3.22-3.38
- Birefringence: 0.024-0.031
Characteristics
- Vivid green rivaling emerald
- Generally available in smaller sizes
- Softer than emerald (H 5.5-6.5)
- Good value for intense green
- Source: Russia (Siberia), Pakistan
Limitations
- Tends to be dark in larger sizes
- Relatively soft for jewellery
- Two cleavage directions
- Best in smaller stones (<1 carat)