How to identify Peridot

To correctly identify Peridot (Olivine (gem variety)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically yellowish-green to pure green, sometimes brownish-green. The intensity of green depends on the iron content.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to oily.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to the touch when polished; rougher in its natural crystal form.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system, often found as stubby prismatic crystals, granular aggregates, or rounded grains in volcanic rocks. Well-formed crystals are relatively rare.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor to distinct in two directions at 90 degrees, but typically exhibits conchoidal fracture rather than clean cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in mafic and ultramafic igneous rocks (basalts, peridotites, dunites), kimberlites, and as xenoliths in volcanic eruptions. Also found in pallasite meteorites.

Key Facts

Hardness

6.5-7 on the Mohs scale

Specific Gravity

3.27-3.48 (typically 3.34)

Crystal System

Orthorhombic

Color

Yellowish-green, olive green, brownish-green

Luster

Vitreous to oily

Transparency

Transparent to translucent

Fracture

Conchoidal

Cleavage

Poor to distinct in two directions (010) and (110), but rarely observed due to conchoidal fracture

Composition

Magnesium iron silicate, (Mg,Fe)2SiO4

Physical characteristics

• Crystal Habit: Prismatic, tabular, granular, massive. Often found as rounded grains in volcanic rocks.
• Cleavage Type: Poor to distinct on {010} and {110}, but fracture is more common.
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous to oily

Explore Peridot