Gem library
Peridot
Green olivine, born in the Earth's mantle
Peridot is the gem variety of olivine, the mineral that makes up most of the Earth's mantle. It is therefore one of the few gems that come from the depths — and one of only two also found in meteorites.
- Hardness (Mohs)
- 6.5 – 7
- Density
- 3.32 – 3.45
- Crystal system
- Orthorhombic
- Refractive index
- 1.650 – 1.703
- Cleavage
- Imperfect on {010}
Mineralogical identity
- Family
- Silicates — olivine group
- Species
- Forsterite-fayalite (olivine)
- Variety
- Peridot (chrysolite)
- Chemical formula
- (Mg,Fe)₂SiO₄
- Crystal system
- Orthorhombic
- Classification
- Semi-precious stone
- Rarity
- Uncommon
- Indicative price
- €20 – 400/ct (Pakistan, large clean sizes)
Etymology
Uncertain origin, probably from the Arabic faridat, «gem». Long called chrysolite, from the Greek «gold stone».
Physical & optical properties
- Hardness (Mohs)
- 6.5 – 7
- Density
- 3.32 – 3.45
- Refractive index
- 1.650 – 1.703
- Birefringence
- 0.035 – 0.038 (strong)
- Cleavage
- Imperfect on {010}
- Fracture
- Conchoidal
- Lustre
- Vitreous to greasy
- Diaphaneity
- Transparent
- UV fluorescence
- None
- Pleochroism
- Weak
- Colours
- olive green, yellow green, bottle green
Formation, geology & history
A gem from the mantle
Olivine is the dominant mineral of the upper mantle, between 30 and 400 km down. Peridot reaches the surface carried by basalts and kimberlites, or as peridotite nodules torn from deep rock and lifted by eruptions. The San Carlos deposit in Arizona works precisely such nodules in a basalt flow. Another, more surprising origin: pallasite meteorites, mixtures of iron-nickel and olivine, contain gem peridot of facetable quality, souvenirs of the core-mantle boundary of a destroyed asteroid. Peridot is thus, with diamond, one of the few gems with an attested extraterrestrial origin.
Zabargad, the pharaohs' island
The island of Zabargad (St John's) in the Red Sea supplied the world's finest peridot for more than three millennia. The Egyptians worked its veins from 1500 BC under military guard; the Romans called it topazos, which permanently muddled the terminology and explains why the word topaz now denotes a different stone. Many «emeralds» in medieval European treasuries are in fact Zabargad peridots: the 200 carats of green gems on the Shrine of the Three Kings in Cologne Cathedral are the most famous example.
Recognising a peridot
Its strong birefringence (0.035) is its most characteristic trait: through a faceted stone, the edges of opposite facets appear clearly doubled under a loupe. Its colour is always green tinged with yellow — peridot exists neither in bluish green nor pure green, because the colour comes from iron, an essential constituent rather than a trace. Typical inclusions are fracture discs called lily pads, with a black chromite crystal at the centre. Its modest hardness and imperfect cleavage call for care in rings.
How to recognise it
- Doubled facet edgesUnder a 10× loupe through the table, the pavilion facet edges appear double: peridot's birefringence is among the strongest of common gems.
- Always yellowish greenNo natural peridot is bluish or pure green. A true emerald-green stone is a tsavorite, an emerald or glass.
- Lily-pad inclusionsCircular tension discs with a small black crystal at the centre are typical and constitute a natural signature.
Imitations, treatments & confusions
- Olive-green glassBubbles, no birefringence, a softer lustre, blunted edges. Very common in antique costume jewellery.
- Confusion with industrial olivine and green YAGLaboratory simulants lack birefringence. The doubled-edge test is decisive.
- Sold as emeraldHistorically frequent, and often unintentional in old collections. Emerald is bluish green, peridot yellowish green, and their birefringences differ greatly.
Deposits & origins
Pakistan (Kohistan, Sapat valley — the finest, up to 100 carats), Egypt (Zabargad island in the Red Sea, a historic deposit worked since 1500 BC), Burma, United States (Arizona, San Carlos reservation), China, Norway, and pallasite meteorites
Care & precautions
- Warm soapy water and a soft brush, brief rinsing. Avoid hot water.
- Very sensitive to thermal shock: peridot fractures easily if moved from hot to cold. Do not wear it in the kitchen.
- No ultrasonic cleaning, no steam: the heat-plus-vibration combination is the leading cause of broken peridot in workshops.
- Sensitive to acids, including acidic sweat: wipe it after wearing.
Traditions & crystal healing
- Chakras
- Heart · solar plexus
- Zodiac signs
- Leo · Virgo · Libra
- Element
- Earth · Fire
- Month
- August
Tradition links it to solar light and clarity of heart: it is said to dispel melancholy, encourage gratitude and lighten resentment. The Egyptians called it the «gem of the sun» and wore it as an amulet against night terrors, a use attested in the papyri.
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
Peridot or emerald?
Colour settles it: peridot is olive green tinged with yellow, emerald bluish green. Peridot also clearly doubles edges under a loupe, and costs far less.
Is peridot fragile?
Its hardness of 6.5-7 is decent, but it fears thermal shock and acids. In an everyday ring, prefer a protective setting and take it off for washing up and cooking.
Why did the Romans call it topaz?
Because the Greeks called the island of Zabargad Topazos. The name later migrated to a different stone, creating a two-thousand-year terminological confusion.