How to identify Serpentine

To correctly identify Serpentine (Mg3Si2O5(OH)4), 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 shades of green (light to dark, olive, yellowish-green, bluish-green), but can also be yellowish, brownish, black, or white. Often mottled or veined.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Greasy, waxy, silky (especially chrysotile), or dull.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth, soapy, or slippery to the touch. Massive varieties can be fine-grained to cryptocrystalline. Fibrous varieties (chrysotile) are soft and flexible.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Rarely forms distinct crystals. Usually massive, platy (antigorite, lizardite), or fibrous (chrysotile). Antigorite often forms lamellar or platy aggregates. Lizardite is typically fine-grained and massive. Chrysotile forms flexible, silky fibers.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect basal cleavage in antigorite and lizardite, though often not observed in massive forms. Chrysotile exhibits fibrous parting rather than true cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Predominantly found in serpentinites, which are metamorphic rocks derived from the hydrothermal alteration of ultramafic igneous rocks (peridotites, dunites) in oceanic crust, subduction zones, and orogenic belts. Also occurs in contact metamorphic aureoles around igneous intrusions into dolomitic limestones.

Key Facts

Hardness

2.5-5 on the Mohs scale (varies by polymorph; chrysotile is ~2.5-3, antigorite ~3.5-4, lizardite ~2.5-3.5)

Specific Gravity

2.5-2.6 g/cm³

Crystal System

Monoclinic (antigorite, chrysotile), Trigonal (lizardite)

Color

Green (most common), yellow, brown, black, white

Luster

Greasy, waxy, silky (chrysotile), dull

Transparency

Translucent to opaque

Fracture

Conchoidal to splintery (massive forms), fibrous (chrysotile)

Cleavage

Perfect basal cleavage (001) in antigorite and lizardite, but often not visible in massive forms. Chrysotile exhibits fibrous parting.

Composition

Hydrous magnesium iron phyllosilicate

Physical characteristics

• Crystal Habit: Massive, platy, lamellar, fibrous (chrysotile), pseudomorphic after olivine or pyroxene.
• Cleavage Type: Perfect basal (001) in antigorite and lizardite, but often indistinct or not observed. Fibrous parting in chrysotile.
• Fracture Type: Conchoidal to splintery in massive varieties; fibrous in chrysotile.
• Tenacity: Brittle to flexible (chrysotile fibers are flexible and inelastic).
• Luster Type: Greasy, waxy, silky, dull.

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