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Jade is a cultural term referring to two distinct silicate minerals: nephrite and jadeite. Both are exceptionally tough and durable, making them ideal for carving. They exhibit a wide range of colors, most commonly green, but also white, lavender, yellow, orange, brown, and black. While visually similar, they differ significantly in their chemical composition, crystal structure, and physical properties.
Jak identifikovat
- Barva
- Nephrite: typically creamy white, spinach green, dark green, grey, brown, black. Jadeite: more vibrant greens (emerald to apple green), lavender, white, yellow, orange, black. Both can be mottled or variegated.
- Lesk
- Vitreous to greasy, sometimes waxy.
- Textura
- Fine-grained, interlocking fibrous (nephrite) or granular (jadeite) texture, resulting in exceptional toughness. Smooth to the touch when polished.
- Tvar krystalů
- Nephrite: cryptocrystalline, felted mass of interlocking fibers. Jadeite: granular to fibrous aggregates, rarely well-formed crystals.
- Štěpnost
- Nephrite: perfect on {110} (amphibole cleavage, 56° and 124°). Jadeite: perfect on {110} (pyroxene cleavage, 87° and 93°). Due to the fine-grained nature, cleavage is rarely observed in hand specimens.
- Geologické prostředí
- Nephrite: formed by metasomatism of ultramafic rocks (serpentinites) or dolomitic limestones. Jadeite: formed in high-pressure, low-temperature metamorphic environments, typically associated with serpentinite in subduction zones.
Klíčová fakta
- Tvrdost: Nephrite: 6-6.5 (Mohs); Jadeite: 6.5-7 (Mohs)
- Hustota (specifická hmotnost): Nephrite: 2.90-3.03; Jadeite: 3.30-3.38
- Krystalová soustava: Nephrite: Monoclinic; Jadeite: Monoclinic
- Barva: Wide range, predominantly green, white, lavender, yellow, orange, black.
- Lesk: Vitreous to greasy, sometimes waxy.
- Průhlednost: Translucent to opaque, rarely semi-transparent.
- Lom: Splintery (nephrite) to granular/uneven (jadeite), very tough.
- Štěpnost: Perfect prismatic (nephrite: 56°/124°; jadeite: 87°/93°), but rarely observed due to fine-grained nature.
- Složení: Nephrite: Calcium magnesium iron silicate; Jadeite: Sodium aluminum silicate.
Rychlá kontrola
- Barva: Green, white, lavender, yellow, orange, black (variable)
- Lesk: Vitreous to greasy/waxy
- Vryp: White
Fyzikální vlastnosti
- Krystalový habitus: Nephrite: Cryptocrystalline, felted mass of interlocking fibers. Jadeite: Granular to fibrous aggregates, massive.
- Typ štěpnosti: Perfect prismatic, but rarely visible in hand specimens due to fine-grained nature.
- Typ lomu: Splintery (nephrite), granular to uneven (jadeite). Extremely tough.
- Houževnatost: Extremely tough (resistant to breaking and chipping).
- Typ lesku: Vitreous to greasy, waxy.
Vznik
Jadeite forms under high-pressure, low-temperature metamorphic conditions, typically in subduction zones. Nephrite forms through regional metamorphism of ultramafic rocks (serpentinites) or dolomitic limestones.
Využití
Historically and currently used for carving, jewelry, ornamental objects, tools, and ritualistic artifacts. Highly prized in many cultures, particularly in East Asia.
Stáří a rozšíření
Varies greatly depending on geological setting, from Precambrian to Cenozoic.
Kde najít
Myanmar (Burma)
Primary source of gem-quality jadeite, particularly the highly prized 'Imperial Jade'. Occurs in alluvial deposits and in situ within serpentinite bodies.
Canada (British Columbia)
Major source of nephrite jade, found in large boulders and in situ deposits associated with serpentinite.
Russia (Sayan Mountains)
Significant deposits of nephrite, often with attractive green colors.
China (Xinjiang, Liaoning)
Historical source of nephrite ('Hetian Jade'), found in alluvial deposits and primary occurrences.
Guatemala
Source of jadeite, including rare blue and black varieties, historically used by Mayan civilizations.
USA (Wyoming, California, Alaska)
Nephrite deposits are found in several states, often associated with ultramafic rocks.
New Zealand (South Island)
Known for its nephrite ('Pounamu' or 'Greenstone'), culturally significant to the Māori people. Found in riverbeds and glacial deposits.
Tipy pro hledání
Look for specific geological settings
For nephrite, search in areas with serpentinite outcrops, altered ultramafic rocks, or dolomitic marbles. For jadeite, focus on high-pressure metamorphic terrains, often associated with serpentinite in subduction zones.
Check riverbeds and alluvial deposits
Both nephrite and jadeite are extremely tough and resistant to weathering, so they can be found as rounded pebbles and boulders in riverbeds downstream from their primary sources.
Perform a scratch test (carefully)
Jadeite (Mohs 6.5-7) is harder than nephrite (Mohs 6-6.5). Neither should be easily scratched by a steel knife (Mohs 5.5). This can help differentiate from softer look-alikes like serpentine.
Assess toughness, not just hardness
Jade's defining characteristic is its exceptional toughness due to its interlocking fibrous structure. It is very difficult to break, even with a hammer. This is a key differentiator from many brittle minerals.
Observe translucency and luster
High-quality jade often exhibits a waxy to vitreous luster and can be translucent, especially in thinner sections. Serpentine, a common simulant, often has a more greasy or resinous luster and can be more opaque.
Podobné kameny
Serpentine
Serpentine group minerals (e.g., Mg3Si2O5(OH)4)
Také známý jako: Bowenite, Antigorite, Lizardite
Chrysoprase
SiO2
Také známý jako: Green chalcedony
Aventurine
SiO2
Také známý jako: Green quartz
Hydrogrossular Garnet
Ca3Al2(SiO4)3-x(OH)4x
Také známý jako: Transvaal Jade
Vědecká klasifikace
- Třída minerálu
- Silicates
- Skupina
- Nephrite: Amphibole group (actinolite-tremolite series); Jadeite: Pyroxene group
- Krystalová soustava
- Monoclinic
- Chemický vzorec
- Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2; Jadeite: NaAlSi2O6
- Složení
- Nephrite: Hydrous calcium magnesium iron silicate; Jadeite: Sodium aluminum silicate.
Prozkoumat Jade
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