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Jadeite is a pyroxene mineral, a sodium-aluminum inosilicate, known for its exceptional toughness and often vibrant green color. It is one of the two minerals commonly referred to as 'jade' (the other being nephrite). Jadeite is generally more valuable and rarer than nephrite, especially the translucent, emerald-green variety known as 'Imperial Jade'.
How to Identify
- Color
- Most commonly green (ranging from pale to emerald green), but can also be white, lavender, blue, pink, brown, red, orange, or black. Often mottled or variegated.
- Luster
- Vitreous to greasy, sometimes pearly on cleavage surfaces.
- Texture
- Typically fine-grained, interlocking fibrous or granular aggregates, giving it exceptional toughness.
- Crystal Form
- Rarely forms distinct crystals; usually found as massive, granular, or fibrous aggregates. When crystals are present, they are typically prismatic.
- Cleavage
- Two distinct cleavages at approximately 87° and 93° (pyroxene cleavage), but rarely observed in massive material due to its fine-grained nature.
- Geological Environment
- High-pressure, low-temperature metamorphic rocks (blueschists, eclogites) in subduction zones. Often found in serpentinite mélanges.
Key Facts
- Hardness: 6.5-7 on the Mohs scale
- Specific Gravity: 3.30-3.38
- Crystal System: Monoclinic
- Color: Variable, most famously green, but also white, lavender, blue, pink, brown, red, orange, black
- Luster: Vitreous to greasy
- Transparency: Translucent to opaque, rarely transparent
- Fracture: Splintery to granular, very tough
- Cleavage: Perfect on {110} at 87° and 93°, but rarely observed in massive material
- Composition: Sodium aluminum inosilicate (NaAlSi2O6)
Quick Check
- Color: Green, white, lavender, blue, pink, brown, red, orange, black (often mottled)
- Luster: Vitreous to greasy
- Streak: White
Physical Characteristics
- Crystal Habit: Typically massive, granular, or fibrous aggregates; rarely as distinct prismatic crystals.
- Cleavage Type: Perfect in two directions at nearly 90 degrees (87° and 93°), characteristic of pyroxenes.
- Fracture Type: Splintery to granular, due to its interlocking microstructure.
- Tenacity: Extremely tough, making it resistant to breaking and chipping.
- Luster Type: Vitreous to greasy, sometimes pearly on cleavage surfaces.
Formation
Jadeite forms under high-pressure, low-temperature metamorphic conditions, typically in subduction zones where oceanic crust is thrust beneath continental crust. It is a characteristic mineral of blueschist and eclogite facies metamorphism. It forms from the alteration of sodium-rich plagioclase feldspar or other aluminous silicates in the presence of fluids.
Usage
Primarily used as a gemstone, particularly in East Asian cultures where it holds significant cultural and spiritual value. It is carved into jewelry, ornaments, and sculptures. Due to its toughness, it was historically used for tools and weapons by various indigenous cultures.
Age Distribution
Typically associated with subduction zone metamorphism, thus found in rocks ranging from Mesozoic to Cenozoic in age.
Where to Find
Myanmar (Burma)
The primary source of gem-quality jadeite, particularly the highly prized 'Imperial Jade'. Found in alluvial deposits and in situ in serpentinite-associated rocks in the Kachin State.
Guatemala
Historically significant source, rediscovered in the late 20th century. Found in metamorphic rocks associated with ancient subduction zones.
Japan
Occurs in Itoigawa, Niigata Prefecture, associated with serpentinite and blueschist facies rocks.
Russia
Found in the Polar Urals and other regions, often associated with ophiolite complexes.
California, USA
Occurs in various localities, including Clear Creek and New Idria, San Benito County, typically in serpentinite-rich environments.
Finding Tips
Geological Context
Focus searches in areas known for high-pressure, low-temperature metamorphic rocks, especially blueschist facies terrains and serpentinite mélanges, which are characteristic of ancient or active subduction zones.
Associated Minerals
Look for jadeite in association with other minerals indicative of its formation environment, such as glaucophane, lawsonite, omphacite, albite, and serpentine minerals.
Density Test
Jadeite has a relatively high specific gravity (3.30-3.38). This can be a useful field test to distinguish it from lighter look-alikes like serpentine or quartz.
Toughness
Jadeite is exceptionally tough, meaning it resists breaking and chipping. This can be observed when attempting to break or scratch a specimen (though this should be done carefully to avoid damaging valuable samples).
Color and Luster
While color is variable, the characteristic vitreous to greasy luster and often mottled appearance can be good indicators. Translucency is a key feature of gem-quality material.
Similar Rocks
Nephrite
Ca2(Mg,Fe)5Si8O22(OH)2
Also known as: Mutton Fat Jade
Serpentine
Mg3Si2O5(OH)4
Also known as: Bowenite, Antigorite, Chrysotile
Hydrogrossular Garnet
Ca3Al2(SiO4)3-x(OH)4x
Also known as: Transvaal Jade
Scientific Classification
- Mineral Class
- Inosilicates (Chain Silicates)
- Group
- Pyroxene Group
- Crystal System
- Monoclinic
- Chemical Formula
- NaAlSi2O6
- Composition
- Sodium aluminum silicate
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