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Jadeite is a pyroxene mineral, NaAlSi2O6, and is one of the two minerals commonly known as 'jade' (the other being nephrite). It is highly prized for its exceptional toughness, vibrant colors (especially imperial green), and translucent to opaque appearance. It typically occurs as an aggregate of interlocking, fine-grained crystals, forming a dense, compact rock. The most valuable varieties are translucent and emerald green, colored by chromium.
How to Identify
- Color
- Most commonly green (ranging from pale to dark emerald green, often mottled), but can also be white, lavender, blue, black, brown, red, or orange. The most prized color is 'imperial jade,' a vivid, translucent emerald green.
- Luster
- Vitreous to greasy, sometimes pearly on cleavage surfaces.
- Texture
- Typically fine-grained, compact, and interlocking, giving it a smooth, waxy feel when polished. Can be granular to fibrous.
- Crystal Form
- Usually massive, granular, or fibrous aggregates. Individual crystals are rarely macroscopic and are typically anhedral.
- Cleavage
- Two distinct cleavages at approximately 87 and 93 (pyroxene cleavage), but rarely observed in massive aggregates due to fine grain size and interlocking texture. Fracture is more common.
- Geological Environment
- High-pressure, low-temperature metamorphic rocks, particularly in serpentinite-associated blueschist facies terrains and within serpentinite mélanges. Often found in veins or lenses within these host rocks.
Key Facts
- Hardness: 6.5-7 on Mohs scale
- Specific Gravity: 3.30-3.38
- Crystal System: Monoclinic
- Color: Variable, most commonly green; also white, lavender, blue, black, brown, red, orange
- Luster: Vitreous to greasy
- Transparency: Translucent to opaque
- Fracture: Splintery to granular, very tough
- Cleavage: Perfect on {110} and {10} at 87 and 93, but rarely observed in massive aggregates
- Composition: Sodium aluminum silicate
Quick Check
- Color: Green, white, lavender, black, blue, brown, red, orange
- Luster: Vitreous to greasy
- Streak: White
Physical Characteristics
- Crystal Habit: Typically massive, granular, or fibrous aggregates; individual crystals are anhedral and microscopic.
- Cleavage Type: Two distinct cleavages at nearly 90 degrees (87 and 93), characteristic of pyroxenes, but often obscured by fine grain size.
- Fracture Type: Splintery to granular, due to its interlocking fibrous or granular texture, contributing to its exceptional toughness.
- Tenacity: Extremely tough (resistant to breaking, chipping, or cracking), making it ideal for carving.
- Luster Type: Vitreous (glassy) to greasy, sometimes waxy on polished surfaces.
Formation
Jadeite forms under high-pressure, low-temperature metamorphic conditions, characteristic of subduction zones. It is typically found in serpentinite-associated metamorphic rocks, often in blueschist facies or within serpentinite mélange. The protoliths are commonly mafic or ultramafic igneous rocks, or sedimentary rocks with appropriate chemical composition, subjected to pressures exceeding 10 kbar and temperatures between 200-400 C.
Usage
Primarily used as a gemstone for carving, jewelry, and ornamental objects. Historically, it was also used for tools and weapons due to its exceptional toughness.
Age Distribution
Typically Mesozoic to Cenozoic, associated with subduction zones.
Where to Find
Myanmar (Burma)
The primary source of gem-quality jadeite, particularly the highly prized 'imperial jade.' Found in the Uru River region of Kachin State.
Guatemala
Historically significant source, rediscovered in the Motagua Valley. Produces a range of colors, including lavender and a rare blue jadeite.
Japan
Occurrences in Itoigawa, Omi, and Kotaki regions, primarily in alluvial deposits and in situ within serpentinite bodies.
Russia
Found in the Polar Urals and other regions, often associated with ophiolite complexes.
California, USA
Minor occurrences in Mendocino and San Benito counties, typically lower quality than Burmese material.
Kazakhstan
Known for various colors of jadeite.
Finding Tips
Geological Context
Focus on areas known for high-pressure, low-temperature metamorphic rocks, especially those associated with serpentinites, blueschists, and subduction zones. Alluvial deposits downstream from such areas can also yield jadeite pebbles and boulders.
Appearance and Feel
Look for dense, fine-grained, tough material with a waxy to vitreous luster. It often has a distinctive 'ring' when struck lightly. The specific gravity is noticeably higher than many common rocks.
Hardness Test
Jadeite has a Mohs hardness of 6.5-7, meaning it can scratch glass and steel but will not be scratched by them. This helps differentiate it from softer look-alikes like serpentine.
Specific Gravity Test
Jadeite has a specific gravity of 3.30-3.38. This is a crucial diagnostic test to distinguish it from nephrite (SG 2.90-3.00) and other simulants. A simple 'heft' test can often give an initial indication.
Refractive Index
For gemological identification, a refractometer can be used to measure the refractive index, which is typically 1.65-1.67 for jadeite (spot reading).
Spectroscopy
Advanced identification involves Raman spectroscopy or FTIR to confirm the mineral's chemical structure.
Safety Warning
Jadeite itself is not hazardous. However, some associated rocks in its geological environment, such as serpentinites, may contain asbestos minerals (e.g., chrysotile, antigorite, tremolite-actinolite). When collecting in such areas, avoid disturbing or breaking friable fibrous minerals. Always wear appropriate personal protective equipment (PPE), including dust masks, if there's a risk of airborne particles. Wash hands thoroughly after handling raw specimens. Do not ingest any rock or mineral material.
Similar Rocks
Nephrite Jade
Nephrite (mineral, a variety of actinolite-tremolite)
Also known as: Nephrite
Serpentine
Serpentine Group Minerals
Also known as: Bowenite, Antigorite, Chrysotile
Hydrogrossular Garnet
Hydrogrossular
Also known as: Transvaal Jade
Chrysoprase
Chalcedony (a variety of quartz)
Also known as: Australian Jade
Scientific Classification
- Mineral Class
- Silicate
- Group
- Pyroxene Group
- Crystal System
- Monoclinic
- Chemical Formula
- NaAlSi2O6
- Composition
- Sodium aluminum inosilicate
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