Pyroxene Group
Pyroxene group gems including jadeite, spodumene (kunzite, hiddenite), and diopside (chrome diopside) with properties and identification.
By Fabian Moor
Last updated
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
Major Sources
- Myanmar: Premier source; Imperial green [1]
- 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 |
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⁺) [2]
- 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)
Identification Summary
References
- ↑ 1. Hughes, R.; Galibert, O.; Bosshart, G.; Ward, F.; Oo, T.; Smith, C.; Sun, T.; Harlow, G. (2000). Burmese Jade: The Inscrutable Gem. Gems & Gemology, 36(1), 2–26. DOI: 10.5741/gems.36.1.2.
- ↑ 2. Fritsch, E.; Rossman, G. (1987). An Update on Color in Gems. Part 1: Introduction and Colors Caused by Dispersed Metal Ions. Gems & Gemology, 23(3), 126–139. DOI: 10.5741/gems.23.3.126.