Gem library
Lapis lazuli
Afghan midnight blue, sown with gold
Lapis lazuli is not a mineral but a rock: blue lazurite mixed with white calcite and golden pyrite. Extracted from the same Afghan mines for six millennia, it gave Western painting its most precious pigment, ultramarine.
- Hardness (Mohs)
- 5 – 6
- Density
- 2.7 – 2.9
- Crystal system
- Cubic
- Refractive index
- 1.50 (average)
- Cleavage
- None (rock)
Mineralogical identity
- Family
- Metamorphic rock (lazurite + calcite + pyrite)
- Species
- Lazurite (main component)
- Variety
- Lapis lazuli
- Chemical formula
- (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₂ — lazurite
- Crystal system
- Cubic (lazurite) — polycrystalline rock
- Classification
- Semi-precious stone (ornamental rock)
- Rarity
- Uncommon
- Indicative price
- €1 – 30/ct
Etymology
From the Latin lapis, «stone», and the Persian lazhward, blue — the same root as «azure». Literally: the blue stone.
Physical & optical properties
- Hardness (Mohs)
- 5 – 6
- Density
- 2.7 – 2.9
- Refractive index
- 1.50 (average)
- Cleavage
- None (rock)
- Fracture
- Splintery
- Lustre
- Dull to waxy
- Diaphaneity
- Opaque
- UV fluorescence
- Weak
- Pleochroism
- None
- Colours
- ultramarine blue, midnight blue, violet blue
Formation, geology & history
One rock, three minerals
The blue comes from lazurite, a feldspathoid of the sodalite group whose colour is due to polysulphide ions — a rare mechanism responsible for that unique hue. White calcite appears as veins and clouds: the more abundant it is, the less fine the stone. Golden pyrite is prized as fine flecks that make the surface sparkle, but coarse masses of it devalue the stone. Ideal lapis, called Afghan or «Persian» quality, is a deep even ultramarine with a discreet sprinkling of pyrite. Chilean lapis, more affordable, shows much calcite and a duller blue.
Ultramarine, a pigment dearer than gold
Grinding lapis yields only a bluish grey; isolating the blue takes a long extraction by kneading with wax and lye. The process, developed in the Middle East and imported to Europe in the twelfth century, made the pigment costlier than gold by weight: altarpiece commission contracts specified how much ultramarine to use. Reserved for the Virgin's mantle and for skies, it also explains why so many painters had to do without. In 1826 Jean-Baptiste Guimet perfected artificial ultramarine and ended six centuries of Afghan monopoly on blue.
Six thousand years of trade
The mines of Sar-e-Sang, in Afghan Badakhshan at 2,500 metres, already supplied Sumer and predynastic Egypt. Lapis travelled the Oxus route to Mesopotamia and the Indus. It is found in the royal tombs of Ur, on Tutankhamun's mask, in the Standard of Ur. No other deposit has played a comparable role in the history of exchange. Even today, most fine lapis comes from those same veins, worked in difficult conditions.
How to recognise it
- Golden pyrite flecksTiny irregular metallic flakes are the best sign of authenticity. A perfectly pure blue with no inclusions is often dyed jasper or glass.
- Deep matt blueLapis has a muted, velvety blue, never glossy or electric. A garish saturation suggests dye.
- Hardness 5-6It scratches glass with difficulty and is marked by a steel file. A «lapis» scratched by a fingernail is dyed howlite.
Imitations, treatments & confusions
- Dyed jasper («Swiss lapis», «German lapis»)Bluish jasper dyed with ferrocyanide. No pyrite, an over-uniform blue, a blue deposit on cotton soaked in acetone.
- Sodalite sold as lapisVery frequent: sodalite is more violet, veined with white, pyrite-free and less dense. It is worth five to ten times less.
- Reconstituted material and glass («Gilson stone»)Agglomerated lazurite powder or glass with copper flakes. Over-regular pattern, flakes too large and too golden, lightness.
Deposits & origins
Afghanistan (Sar-e-Sang, Kokcha valley, worked for over 6,000 years and still the world benchmark), Chile (Ovalle, paler and white-flecked), Russia (Lake Baikal), Pakistan, Myanmar, Canada
Care & precautions
- Never soak: the calcite in lapis is attacked by acids and the stone is slightly porous.
- A barely damp soft cloth, dried at once. No solvents, no household products.
- Much commercial lapis is waxed or oiled to deepen the colour: hot water and solvents remove that treatment.
- No ultrasonic cleaning, no steam. Protect it from impact: the rock is fragile in thin sections.
Traditions & crystal healing
- Chakras
- Third eye · throat
- Zodiac signs
- Sagittarius · Pisces
- Element
- Air · Water
- Month
- September (secondary)
Tradition makes it the stone of truth and right speech: it is said to help say what is, carry authority without harshness, and clarify judgement. It is one of the few stones whose ritual use is documented without interruption since Sumer, where it represented the night sky.
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
Lapis lazuli or sodalite?
Sodalite is more violet, lighter, veined with white and free of pyrite. Lapis is a deep ultramarine with golden flecks. Prices differ by a factor of five to ten.
Is my lapis dyed?
Rub a discreet area with cotton soaked in acetone: a blue deposit reveals dye. Natural lapis always keeps some calcite and pyrite nuances.
Can it be worn every day?
As a pendant or earrings, yes. As a ring, with reservations: hardness only 5-6, sensitive to acids and sweat, and the polish dulls over time.