Gem library
Chrysoprase
The nickel chalcedony
Chrysoprase is green chalcedony, coloured by nickel. It is the most precious of the chalcedonies, and the only one whose colour comes from neither iron nor chromium. Its translucent apple green has earned it the misleading nickname «Australian jade».
- Hardness (Mohs)
- 6.5 – 7
- Density
- 2.58 – 2.64
- Crystal system
- Trigonal
- Refractive index
- 1.530 – 1.539
- Cleavage
- None
Mineralogical identity
- Family
- Chalcedony — silica group
- Species
- Quartz
- Variety
- Chrysoprase (nickel-bearing chalcedony)
- Chemical formula
- SiO₂ + Ni
- Crystal system
- Trigonal (microcrystalline aggregate)
- Classification
- Semi-precious stone
- Rarity
- Uncommon
- Indicative price
- €10 – 80/ct
Etymology
From the Greek khrysós, «gold», and prason, «leek»: golden leek-green. The name is mentioned by Pliny the Elder and appears among the gems of the heavenly Jerusalem in Revelation.
Physical & optical properties
- Hardness (Mohs)
- 6.5 – 7
- Density
- 2.58 – 2.64
- Refractive index
- 1.530 – 1.539
- Birefringence
- up to 0.004
- Cleavage
- None
- Fracture
- Conchoidal to splintery
- Lustre
- Vitreous to waxy
- Diaphaneity
- Translucent
- UV fluorescence
- None
- Pleochroism
- None
- Colours
- green, apple-green, yellow-green
Formation, geology & history
Formation and colour
Chrysoprase forms by the weathering of nickel-rich ultrabasic rocks — peridotites, serpentinites — under a tropical climate with marked seasons. Surface water leaches the nickel, which concentrates in laterites, then precipitates with silica in the fissures beneath. The nickel sits not in the quartz lattice but as extremely fine inclusions of nickel-bearing silicates — kerolite, pimelite — dispersed through the chalcedony. That explains both its milky opacity and its sensitivity: the colour rests on hydrated inclusions, not on an ion locked in a stable crystal.
An antique gem
Chrysoprase is one of the best-documented gems of antiquity. Greeks and Romans used it for intaglios and cameos, Pliny describes it, and the Szklary deposit in Silesia was worked from the Middle Ages to the nineteenth century. Frederick II of Prussia made it a court stone: the chapel at Sanssouci and several pieces of his furniture are decorated with it. It is also, most likely, the stone tradition attributes to Alexander the Great, said to have worn it at his belt as a talisman of victory — a legendary detail, but one that testifies to this chalcedony's ancient prestige.
Fragility of the colour
Chrysoprase has a serious and rarely disclosed flaw: it dehydrates. Exposed to sun, dry heat, or simply very dry air over months, it pales and takes on a whitish milky look. The process is sometimes reversible — prolonged immersion in water can restore part of the hue — which distinguishes it from kunzite or larimar, whose loss is permanent. Informed collectors keep their pieces in the shade, and some museums store them in humidity-controlled cases.
How to recognise it
- Uniform translucent apple greenChrysoprase is a clear green, translucent over a few millimetres, without veins or patches. Veined or mottled green points to serpentine, jade or aventurine.
- No visible structureUnder the loupe, chalcedony is homogeneous and microcrystalline: nothing to see. No radiating fibres as in prehnite, no granules as in jadeite, no flakes as in serpentine.
- Hardness 6.5-7It scratches glass decisively and resists steel, unlike softer serpentine, which a needle marks. It is the test that best separates it from its natural imitations.
Imitations, treatments & confusions
- Serpentine and «jade» sold as chrysopraseGreen serpentine is far softer — it scratches with steel — and its lustre is waxy, almost soapy. True jade is denser and tougher. Hardness settles it without instruments.
- Green-dyed chalcedonyVery common. The dye concentrates in micro-fissures: under the loupe you see a network of darker lines, and the colour looks laid on the surface rather than diffused. The green is often too blue.
- Glass and «reconstituted chrysoprase»Glass shows bubbles and perfect homogeneity. Resin-bonded powders are lighter and warm to the touch, with a surface that a steel point scratches.
Deposits & origins
Australia (Marlborough, Queensland — the major source, called «Australian jade»; Yerilla, Western Australia), Poland (Szklary, Lower Silesia — the historic European deposit), Tanzania (Haneti), Brazil, Kazakhstan, South Africa, Russia (Urals)
Care & precautions
- Warm soapy water and a soft brush: chrysoprase does not fear water — quite the opposite.
- Ultrasonic cleaning generally tolerated, but avoid it on fractured or antique pieces.
- Avoid direct sun and prolonged dry heat, which make it pale. A spell in water can sometimes revive the hue.
- Store away from light, in a non-airtight container and away from harder stones.
Traditions & crystal healing
- Chakras
- Heart
- Zodiac signs
- Taurus · Cancer · Libra
- Element
- Earth · Water
- Month
- May
A heart stone in both ancient tradition and contemporary crystal healing, chrysoprase is associated with gentleness, hope and the healing of emotional wounds. The Greeks saw a talisman of victory in it, medieval treatises a remedy for disorders of the sight. It is recommended today as a pendant worn on the sternum, to ease guilt and nostalgia.
The virtues described here belong to tradition and cultural heritage. They are in no way medical advice and never replace a consultation.
Frequently asked questions
My chrysoprase has paled — is it permanent?
Not always, and that is its peculiarity. Colour loss comes from dehydration of the nickel-bearing inclusions; a prolonged spell in water sometimes restores part of the hue. Prevention is better: avoid the sun.
Chrysoprase or jade?
Chrysoprase is a silica chalcedony, jade a pyroxene or an amphibole. Jade is denser and above all far tougher. The name «Australian jade» given to chrysoprase is purely commercial and misleading.
Why is it the most expensive chalcedony?
Because nickel is rare in it: it requires lateritic weathering on ultrabasic rock, far more restrictive than the simple silica circulation that produces agates and carnelians. Fine uniform greens are genuinely uncommon.