How to identify Serpentine

To correctly identify Serpentine (Serpentinite (rock)), 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 green, olive green, dark green, greenish-black), often mottled or variegated. Can also be yellowish-green, brownish-green, or rarely reddish.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Greasy, waxy, silky (especially fibrous varieties), or dull.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Massive, platy, fibrous, or granular. Often feels smooth or soapy to the touch. May exhibit slickensides (polished, striated surfaces) due to tectonic movement.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Individual serpentine minerals are typically microscopic, forming aggregates. Macroscopically, it appears massive, platy, or fibrous. Chrysotile (a serpentine mineral) forms flexible, silky fibers.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Serpentine minerals have perfect cleavage in one direction (basal), but in massive serpentinite, this is rarely observed macroscopically. Instead, the rock tends to fracture irregularly or splinter.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Commonly found in ophiolite complexes (remnants of oceanic crust and upper mantle obducted onto continents), suture zones, fault zones, and areas of regional metamorphism where ultramafic rocks have been hydrated. Often associated with peridotite, gabbro, and basalt.

Key Facts

Hardness

2.5 - 4 on Mohs scale (for serpentine minerals, the rock itself can vary)

Specific Gravity

2.5 - 2.8 g/cm³

Crystal System

Monoclinic (for antigorite, lizardite, chrysotile)

Color

Green, yellowish-green, brownish-green, greenish-black

Luster

Greasy, waxy, silky, dull

Transparency

Translucent to opaque

Fracture

Conchoidal, splintery, or uneven

Cleavage

Perfect basal cleavage in individual serpentine minerals, but rarely observed in massive rock; rock typically fractures irregularly.

Composition

Hydrous magnesium iron phyllosilicate minerals (Mg,Fe)₃Si₂O₅(OH)₄

Physical characteristics

• Crystal Habit: Massive, platy, fibrous (chrysotile), lamellar (antigorite), microcrystalline (lizardite).
• Cleavage Type: Perfect {001} in individual serpentine minerals, but not typically observed in the rock.
• Fracture Type: Conchoidal, splintery, or uneven.
• Tenacity: Flexible (chrysotile), sectile, or brittle.
• Luster Type: Greasy, waxy, silky, dull.

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