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

Pyroxenes are single-chain inosilicates crystallising in the monoclinic system,
producing three gem-significant species: jadeite, spodumene, and diopside. Jadeite
(NaAlSi₂O₆), the more valuable of the two jade minerals, occurs as an interlocking
microcrystalline aggregate with spot RI 1.654–1.667, SG 3.30–3.38, and hardness
6.5–7 Mohs; these properties reliably separate it from nephrite (RI 1.606–1.632,
SG 2.90–3.02) and serpentine simulants (SG 2.5–2.6). [1] Spodumene
(LiAlSi₂O₆) provides kunzite (manganese-pink, RI 1.660–1.676, strong pleochroism and
orange-pink phosphorescence) and rare chromium-coloured hiddenite (intense green).
Chrome diopside (CaMgSi₂O₆) from Siberia offers Cr³⁺-driven vivid green at accessible
prices, with RI 1.675–1.701 and SG 3.22–3.38. All pyroxene gems share good to perfect
cleavage in two directions at approximately 87°, a durability consideration in ring
settings. Fine Imperial jadeite (vivid chromium-green, semi-transparent, from Myanmar's
Hpakant mines) is among the world's most commercially valuable gem materials; top
cabochons have exceeded $3 million per carat at Hong Kong auction. [2]
[3]

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 [1]
  • Value: Can exceed fine emerald prices

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

Treatments

Jadeite undergoes various treatments:

  • Type A: Natural, untreated (most valuable)
  • Type B: Bleached and polymer-impregnated [1]
  • Type B+C: Bleached, dyed, and impregnated
  • Type C: Dyed (less common alone)

Infrared spectroscopy detects polymer impregnation. [1]

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⁺) [3]
  • 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

Key features for pyroxene identification:

  • Jadeite: Spot RI ~1.66; SG 3.34; aggregate structure
  • Kunzite/hiddenite: RI 1.660–1.676; strong pleochroism; cleavage
  • Chrome diopside: RI 1.675–1.701; Cr spectrum
  • All: Monoclinic; good to perfect cleavage

References

  1. ↑ 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. ↑ 2. Read, P. (2008). Gemmology (3rd ed.). Butterworth-Heinemann. ISBN: 978-0-7506-6449-3. DOI: 10.4324/9780080507224.
  3. ↑ 3. 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.

Related Topics

Physical PropertiesOptical PropertiesAmphibole Group (Nephrite)