How to identify Nephrite Jade

To correctly identify Nephrite Jade (Nephrite (a variety of actinolite or tremolite)), 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

   Ranges from creamy white ('mutton fat jade') to various shades of green (light to dark, often spinach green), grey, yellow, brown, and black. Color is often uniform but can be mottled or banded.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Typically greasy to waxy on unpolished surfaces, becoming vitreous to sub-vitreous when polished.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Microcrystalline to cryptocrystalline, with a characteristic interlocking fibrous texture that contributes to its extreme toughness. Feels smooth and cool to the touch.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Does not form macroscopic crystals; rather, it is a dense, compact aggregate of microscopic, felted amphibole fibers. Macroscopic appearance is massive.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Nephrite itself does not exhibit macroscopic cleavage due to its interlocking fibrous structure. The individual tremolite/actinolite crystals within the aggregate possess two perfect cleavages at approximately 56° and 124°, but these are not observable in the bulk material.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Primarily found in serpentinized ultramafic rocks (e.g., altered peridotites, dunites) and less commonly in metasomatized dolomitic limestones, typically associated with convergent plate boundaries, ophiolite complexes, and contact metamorphic aureoles.

Key Facts

Hardness

6-6.5 (Mohs scale)

Specific Gravity

2.90-3.03

Crystal System

Monoclinic (individual crystals, but aggregate is massive)

Color

White, cream, various shades of green, grey, yellow, brown, black

Luster

Greasy to waxy (unpolished), vitreous to sub-vitreous (polished)

Transparency

Translucent to opaque

Fracture

Splintery to conchoidal (due to fibrous nature)

Cleavage

None observed in bulk material (perfect {110} in individual amphibole crystals)

Composition

Calcium magnesium iron silicate hydroxide

Physical characteristics

• Crystal Habit: Massive, compact, microcrystalline to cryptocrystalline aggregate of interlocking fibrous crystals.
• Cleavage Type: Not observable in bulk nephrite; individual tremolite/actinolite crystals have perfect {110} cleavage.
• Fracture Type: Splintery to conchoidal, due to the fibrous and interlocking nature.
• Tenacity: Extremely tough (resists breaking and chipping), but brittle.
• Luster Type: Greasy to waxy on rough surfaces, vitreous to sub-vitreous on polished surfaces.

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