Gem library
Aventurine
Green quartz flecked with mica
Aventurine is a quartzite strewn with flakes of green mica (fuchsite) that catch the light in a discreet glitter: aventurescence. Delightfully, the stone bears the name of the glass that imitated it, not the other way round.
- Hardness (Mohs)
- 6.5 – 7
- Density
- 2.64 – 2.69
- Crystal system
- Trigonal
- Refractive index
- 1.544 – 1.553
- Cleavage
- None
Mineralogical identity
- Family
- Microcrystalline quartz with inclusions
- Species
- Quartz
- Variety
- Aventurine (aventurine quartzite)
- Chemical formula
- SiO₂ + fuchsite (chromian mica)
- Crystal system
- Trigonal (aggregate)
- Classification
- Semi-precious stone (rock)
- Rarity
- Very common
- Indicative price
- €0.20 – 3/ct
Etymology
From the Italian a ventura, «by chance»: in the seventeenth century a Murano glassmaker accidentally dropped copper filings into molten glass and created aventurine glass. The natural stone inherited its imitation's name.
Physical & optical properties
- Hardness (Mohs)
- 6.5 – 7
- Density
- 2.64 – 2.69
- Refractive index
- 1.544 – 1.553
- Cleavage
- None
- Fracture
- Splintery
- Lustre
- Vitreous, aventurescent
- Diaphaneity
- Translucent to opaque
- UV fluorescence
- None
- Pleochroism
- None
- Colours
- green, blue-green, peach, brown
Formation, geology & history
Aventurescence and composition
This is not a single crystal but a rock: a metamorphic quartzite whose quartz grains enclose flat-lying platelets of chromian mica. Each platelet reflects light like a tiny mirror, producing a moving, scaly glitter. The colour comes from the chromium in the fuchsite; hematite or goethite give the peach, orange and brown variants. The coarser the flakes, the more spectacular but also the cruder the sparkle; the finest aventurines have a deep green and a delicate shimmer. Do not confuse it with sunstone, a feldspar with hematite platelets, whose effect is coppery and far livelier.
A stone of volume
Quarried in blocks, aventurine is used above all for turning and decoration: spheres, obelisks, bowls, table tops, but also beads and cabochons. India produces considerable quantities, which explains its trivial price. In jewellery it appears as cabochons and carved pieces, notably in the Chinese tradition where green evokes jade and aventurine serves as an affordable substitute. Hardness 7 and the absence of cleavage make it a very robust material, suited to rings worn daily.
Aventurine glass, a Venetian story
The Murano accident of the seventeenth century produced a glass packed with crystals of metallic copper, so sparkling that the recipe was jealously guarded for generations. It is also called goldstone or star stone. This glass, often midnight blue or golden brown, is distinguished from natural aventurine by its far too regular glitter, a perfectly homogeneous ground and the presence of bubbles. It is not mineral at all, but its history is a genuine piece of glassmaking heritage.
How to recognise it
- Irregular flakesNatural aventurine's glitter is uneven and scattered, with richer zones. A dense, uniform sparkle across the whole surface indicates goldstone glass.
- Heterogeneous groundQuartzite shows tone variations, veins and visible grains. A perfectly smooth green is suspect.
- Coolness and hardnessIt scratches glass and stays cool to the touch. Green serpentine, often confused with it, is scratched by a knife.
Imitations, treatments & confusions
- Goldstone (aventurine glass)Over-regular coppery flakes, usually on a brown or midnight-blue ground, bubbles under the loupe, immediate warmth in the hand. It is glass, not stone.
- Serpentine or dyed quartziteSold as aventurine but with no mica flakes and a lower hardness. No aventurescence at all under a point light.
- Jade substituteAventurine is sometimes sold as jade in tourist circuits. Nephrite jade is denser, tougher, flake-free and a more oily green.
Deposits & origins
India (Mysore, the main world supplier), Brazil, Russia (Urals), Tanzania, Chile, Spain, Austria
Care & precautions
- Warm soapy water and a soft brush: risk-free, the stone is neither porous nor cleavable.
- Prolonged sun can slightly dull the green of the micas; prefer moderate exposure.
- Ultrasonic-safe on sound pieces.
- The polish of large turned pieces is revived with fine paste on felt.
Traditions & crystal healing
- Chakras
- Heart
- Zodiac signs
- Taurus · Libra · Cancer
- Element
- Earth
Nicknamed the stone of luck you create, tradition holds that it helps you seize opportunities and take failure less tragically. It is also credited with soothing the emotions of the heart, especially in children — one of the stones most often recommended for beginners, gentle and with no reputation for excess.
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
Aventurine or sunstone?
Aventurine is a quartzite with green mica flakes and a discreet glitter. Sunstone is a feldspar with hematite or copper platelets and a far livelier, orange, coppery sparkle.
Is goldstone a stone?
No, it is copper glass made in Murano since the seventeenth century. Beautiful and historic, but entirely artificial: its flakes are too regular to fool a trained eye.
Can it be worn in water?
Yes, without problem: hardness 7, no cleavage, no notable porosity. It is one of the easiest stones in the trade to live with.