How to identify Black Jade

To correctly identify Black Jade (Nephrite Jade), 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 black to very dark green, often appearing opaque black. Can have subtle greenish or brownish undertones when viewed under strong light.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Greasy to vitreous when polished; dull to waxy on rough surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth and cool to the touch when polished. Can feel slightly waxy. The fibrous nature is not typically visible to the naked eye but contributes to its toughness.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Massive, compact, and cryptocrystalline (fibrous aggregate). Individual crystals are microscopic and intergrown, forming a dense felted or matted texture.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No distinct cleavage due to its interlocking fibrous structure; exhibits a splintery to conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in metamorphic terrains, particularly in serpentinized ultramafic rocks (e.g., peridotite, dunite) or in contact metamorphic zones where dolomitic limestones have been altered by silica-rich fluids.

Key Facts

Hardness

6-6.5 (Mohs scale)

Specific Gravity

2.9-3.1

Crystal System

Monoclinic (individual actinolite crystals)

Color

Black, dark green, dark grey-green

Luster

Greasy to vitreous

Transparency

Opaque to translucent on thin edges

Fracture

Splintery to conchoidal

Cleavage

None (due to aggregate nature), but individual actinolite crystals have perfect {110} cleavage at 56° and 124°

Composition

Calcium magnesium iron silicate hydroxide (Ca2(Mg,Fe)5Si8O22(OH)2)

Physical characteristics

• Crystal Habit: Massive, compact, fibrous aggregate (cryptocrystalline)
• Cleavage Type: Not observed in massive form; individual actinolite crystals exhibit perfect prismatic cleavage
• Fracture Type: Splintery to conchoidal
• Tenacity: Extremely tough
• Luster Type: Greasy to vitreous

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