Peridot Gemstone Overview

• Gem name: Peridot
• Mineral name: Olivine (gem-quality variety)
• Mineral class: Silicate (nesosilicate)
• Chemical formula: (Mg,Fe)₂SiO₄
• Crystal system: Orthorhombic
• Mohs hardness: 6.5–7
• Color range: Yellow-green, olive green, brownish-green
• Luster: Vitreous
• Streak: White
• Cleavage: Poor
• Fracture: Conchoidal
• Specific gravity: Approximately 3.2–4.3
• Transparency: Transparent
• Common locations: Pakistan, Myanmar, China, United States (Arizona), Egypt
• Uses: Gemstone jewelry
• Similar minerals: Green garnet, chrysoberyl, tourmaline

Naming and Classification

Peridot is the gem-quality variety of olivine, one of the few gemstones that occurs in only one primary color family: green.

The name “peridot” likely comes from Arabic faridat (“gem”) or possibly from an island name where it was historically mined.

Unlike many gemstones, peridot’s color is inherent to its chemical composition, not caused by trace impurities.

Physical and Optical Characteristics

Peridot typically forms as:

• Rounded or irregular grains in rock
• Less commonly as well-formed crystals

Gem-quality peridot is:

• Transparent
• Bright and lively in appearance

Its color ranges from:

• Yellow-green
• Olive green
• Rich lime green

The most valued stones have a vivid green with minimal brown tones.

The luster is vitreous, giving it a bright, glassy appearance. With a hardness of 6.5–7, it is suitable for jewelry but requires some care.

Color Origin

Peridot’s color is caused by:

• Iron (Fe) within the crystal structure

Unlike many gemstones:

• The green color is not due to trace elements
• It is a fundamental part of the mineral’s composition

Higher iron content produces deeper green tones.

Unique Optical Feature

Peridot often shows:

• Double refraction (birefringence)

This can cause:

• Slight doubling of facet edges when viewed closely

This is a useful identifying characteristic.

Chemical Composition and Structure

Peridot (olivine) is composed of:

• Magnesium (Mg)
• Iron (Fe)
• Silicon (Si)

It is a nesosilicate, meaning its structure consists of isolated silica tetrahedra.

The ratio of magnesium to iron determines:

• Color intensity
• Density

Formation and Geological Occurrence

Peridot forms in high-temperature environments, particularly in:

Mantle-Derived Rocks

• Found in peridotite (named after peridot)
• Brought to the surface by volcanic activity

Basaltic Lava Flows

• Forms as crystals within volcanic rocks

Meteorites

• Found in some pallasite meteorites, where it occurs as gem-quality crystals

These origins make peridot one of the few gemstones with both terrestrial and extraterrestrial sources.

Common Locations

Major sources of peridot include:

• Pakistan: Produces high-quality, vivid green stones
• Myanmar (Burma): Historic source
• United States: Arizona (San Carlos Apache Reservation – major producer)
• China: Significant modern production
• Egypt: Ancient source (St. John’s Island / Zabargad)

Arizona is one of the world’s largest producers today.

Uses and Practical Significance

Peridot is primarily used as:

Gemstone

• Rings, earrings, pendants
• Birthstone for August

Historical Use

• Used in ancient Egyptian jewelry
• Sometimes mistaken for emerald in antiquity

Similar and Related Gemstones

Peridot can resemble:

• Green garnet (tsavorite): Typically deeper green
• Tourmaline: Often darker and more varied in color
• Chrysoberyl: Usually more yellowish

Peridot’s distinct olive-green hue and birefringence help distinguish it.

Identification Notes for Collectors

• Look for yellow-green to olive-green transparent stones
• Check hardness (6.5–7)
• Observe glassy luster
• Look for double refraction (doubling effect)
• Consider volcanic or mantle-derived origin

Peridot is a gemstone variety of olivine, recognized for its distinctive green color, volcanic origin, and long history in jewelry, making it one of the most unique and consistently colored gemstones in the mineral world.