Peridot Gemstones – Properties, Origins, Treatments and Buying Guide

Peridot is one of the few gemstones that occurs in only one colour — green — yet it remains one of the most misunderstood and undervalued gems in the trade. Often confused with emerald, tourmaline or even glass, genuine peridot is a naturally occurring magnesium-rich variety of the mineral olivine and has been treasured since ancient times.

In this guide we examine peridot from a professional gemmological and commercial perspective, covering its physical properties, mineralogy, durability, treatments, origins and how to identify high-quality stones.

What Is Peridot?

Peridot is the gem-quality form of olivine, a magnesium iron silicate mineral found primarily in volcanic and mantle-derived rocks. Unlike most gemstones, peridot is not coloured by trace elements — its green colour comes directly from its iron content.

This makes peridot geologically rare: it forms deep in the Earth’s mantle and is brought to the surface by volcanic activity.

Peridot has the chemical formula:

(Mg,Fe)₂SiO₄

This means it is composed primarily of:

• Magensium
• Iron
• Silicon
• Oxygen

The ratio of magnesium to iron determines the colour:

• High magnesium = bright, vivid green
• High iron = darker, brownish or olive green

The finest peridot has a rich green hue with minimal brown or yellow tones.

Peridot belongs to the silicate mineral group, specifically the nesosilicates.
This means its silica tetrahedra exist as isolated units rather than forming chains or sheets.

Its crystal system is orthorhombic, which results in distinct crystal growth patterns and contributes to its natural cleavage directions and optical properties.

Peridot has a unique combination of gemmological properties that distinguish it from look-alikes.

Lustre
Peridot has a vitreous (glassy) lustre. Well-cut stones show a bright, oily shine when clean and well polished.

Transparency
Gem-quality peridot is transparent. Translucent material is used only in carvings or beads.

Refractive index
1.65 – 1.69
Peridot has noticeable double refraction, meaning facet edges often appear doubled when viewed under magnification — a useful identification feature.

Specific gravity
3.27 – 3.37
Heavier than quartz but lighter than garnet or corundum.

Peridot occurs only in green, but the shade varies:

• Yellow-green
• Lime green
• Apple green
• Olive green
• Brownish green (lower quality)

The most valuable stones display a pure, vivid green with no brown or muddy undertone.

Peridot has a Mohs hardness of 6.5 to 7, which makes it noticeably softer than sapphire, ruby or diamond.

It also has:
Poor cleavage
Moderate brittleness

This means peridot can scratch, chip and crack more easily than harder gemstones and is best suited for pendants, earrings and protected ring settings.

Peridot is one of the few gemstones that is almost always sold untreated.

Common treatments: None
Rare and undesirable: Fracture filling and Surface coating

If a seller claims “heated” or “enhanced” peridot, it is usually a warning sign.

Peridot requires gentle handling.

Avoid:

• Ultrasonic cleaners
• Steam cleaning
• Acids and household chemicals
• Sudden temperature changes

Safe cleaning method:

• Warm water
• Mild soap
• Soft brush

Store peridot separately from harder gemstones such as diamond, sapphire, ruby and quartz to avoid scratching.

Important sources of peridot include:

• Pakistan (Kashmir region) – finest vivid green material
• Myanmar (Burma)
• China
• Vietnam
• Tanzania
• Ethiopia
• Sri Lanka
• Arizona, USA

Rare and exotic:

• Meteorites (pallasites) contain peridot crystals formed in space