Jade

Popis

Jade is a cultural term referring to two distinct silicate minerals: nephrite and jadeite. Both are renowned for their extreme toughness, which allowed them to be carved into intricate shapes and used for tools and weapons in prehistoric times. While they share a similar appearance and cultural significance, their chemical compositions, crystal structures, and geological origins are different. Nephrite is a calcium-magnesium-iron silicate, a member of the amphibole group, forming a microcrystalline, felted aggregate of interlocking fibers. Jadeite is a sodium-aluminum silicate, a member of the pyroxene group, forming a granular, interlocking texture. Both exhibit a wide range of colors, most famously green, but also white, lavender, yellow, orange, brown, and black.

Ako identifikovať

Farba

Nephrite: Typically shades of green (from pale to dark forest green), white, cream, grey, black, brown, or yellow. Often mottled or banded. Jadeite: Wider range of colors including emerald green (imperial jade), lavender, white, black, yellow, orange, and brown. Colors are often more vibrant and uniform than nephrite.

Lesk

Greasy to vitreous (waxy to glassy) on polished surfaces. Nephrite tends to be more waxy/greasy, while jadeite can be more vitreous.

Textúra

Nephrite: Fine-grained, felted, interlocking fibrous texture, giving it exceptional toughness. Jadeite: Fine-grained, granular, interlocking texture, also contributing to its toughness.

Tvar kryštálov

Both nephrite and jadeite typically occur as massive, compact aggregates. Individual crystals are microscopic and not visible to the naked eye. Nephrite forms as cryptocrystalline aggregates of amphibole fibers. Jadeite forms as cryptocrystalline aggregates of pyroxene grains.

Štiepateľnosť

Nephrite: Perfect cleavage in two directions at approximately 56° and 124° (characteristic of amphiboles), but rarely observed due to its fibrous, interlocking nature. Jadeite: Perfect cleavage in two directions at approximately 87° and 93° (characteristic of pyroxenes), also rarely observed in massive forms.

Geologické prostredie

Nephrite: Found in serpentinized ultramafic rocks, often associated with contact metamorphic zones or regional metamorphic belts. Also occurs in alluvial deposits derived from these sources. Jadeite: Occurs in high-pressure, low-temperature metamorphic rocks (blueschist facies), typically within serpentinite bodies in subduction zone environments. Also found in alluvial deposits.

Kľúčové fakty

• Tvrdosť: Nephrite: 6-6.5 (Mohs scale) / Jadeite: 6.5-7 (Mohs scale)
• Hustota: Nephrite: 2.90-3.03 g/cm³ / Jadeite: 3.30-3.38 g/cm³
• Kryštálová sústava: Nephrite: Monoclinic / Jadeite: Monoclinic
• Farba: Wide range, most commonly green, white, lavender, black, yellow, orange, brown.
• Lesk: Greasy to vitreous (waxy to glassy)
• Priehľadnosť: Opaque to translucent, rarely semi-transparent.
• Lom: Splintery to granular (Nephrite) / Uneven to splintery (Jadeite)
• Štiepateľnosť: Nephrite: Perfect in two directions at 56° and 124° (rarely observed) / Jadeite: Perfect in two directions at 87° and 93° (rarely observed)
• Zloženie: Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 (calcium-magnesium-iron silicate) / Jadeite: NaAlSi2O6 (sodium-aluminum silicate)

Rýchla kontrola

• Farba: Green, white, lavender, black, yellow, orange, brown (variable)
• Lesk: Greasy to vitreous (waxy to glassy)
• Vryp: White

Fyzikálne charakteristiky

• Habitus kryštálov: Massive, compact, cryptocrystalline aggregates. Nephrite forms felted, interlocking fibrous masses. Jadeite forms granular, interlocking masses.
• Typ štiepateľnosti: Nephrite: Perfect {110} at 56° and 124° / Jadeite: Perfect {110} at 87° and 93°. Both are rarely observed due to the massive, interlocking nature.
• Typ lomu: Nephrite: Splintery to granular / Jadeite: Uneven to splintery.
• Húževnatosť: Extremely tough (due to interlocking microcrystalline structure), making it highly resistant to breaking and chipping.
• Typ lesku: Greasy to vitreous (waxy to glassy)

Vznik

Jade is a term applied to two distinct minerals: nephrite and jadeite. Nephrite forms through regional metamorphism of ultramafic rocks (e.g., serpentinites) or dolomitic limestones, where calcium-magnesium-iron rich fluids react under specific pressure and temperature conditions (typically low to medium grade metamorphism). Jadeite forms under high-pressure, low-temperature metamorphic conditions, characteristic of subduction zones, where oceanic crust is thrust beneath continental crust. It typically occurs in serpentinite-associated metamorphic rocks, often in veins or lenses.

Využitie

Historically and currently highly prized for carving, jewelry, and ornamental objects due to its exceptional toughness and aesthetic appeal. Used in ancient cultures (e.g., Mesoamerican, Chinese, Maori) for tools, weapons, ritual objects, and adornment. Modern uses include high-end jewelry, sculptures, and decorative items.

Rozloženie veku

Varies greatly depending on geological setting, typically associated with ancient subduction zones and serpentinization processes, ranging from Precambrian to Cenozoic.

Kde nájsť

Tipy na hľadanie

Podobné kamene

Vedecká klasifikácia

Trieda minerálu

Silicates

Skupina

Nephrite: Amphibole group (actinolite-tremolite series) / Jadeite: Pyroxene group

Kryštálová sústava

Monoclinic for both nephrite and jadeite

Chemický vzorec

Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 / Jadeite: NaAlSi2O6

Zloženie

Nephrite: Calcium-magnesium-iron silicate hydroxide / Jadeite: Sodium-aluminum silicate

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