Jade: Mineral Varieties, Gemological Classification, and Terminology

Jade is a commercial term encompassing two distinct mineral species with similar appearance but different crystal structures and compositions.

True Jade (Mineralogical Definition)

Variety	Mineral	Composition	Crystal System	Key Properties
Jadeite	Pyroxene	NaAlSi₂O₆	Monoclinic	Harder (6.5–7), denser (3.3–3.5), vitreous luster, rarer, more valuable
Nephrite	Amphibole (actinolite/tremolite series)	Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂	Monoclinic	Tougher (fibrous), softer (6–6.5), less dense (2.9–3.1), greasy luster

Trade Names and Related Materials (Not True Jade)

• Yu (玉) – Chinese term for both jadeite and nephrite; also used for other "beautiful stones"
• Feicui (翡翠) – Chinese term specifically for gem-quality jadeite ("kingfisher jade")
• Chloromelanite – Dark green to black jadeite rich in Fe³⁺/Fe²⁺
• Omphacite – Pyroxene mineral; major component of some jadeite jade
• Kosmochlor – NaCrSi₂O₆; chromium-rich pyroxene in some jadeite
• Jadeite-diopside / Nephrite-jadeite – Intermediate solid-solution rocks
• Pwachite – Not a recognized mineral; likely a misspelling or trade name

Common Simulants and Misnomers

• Serpentine ("New jade," "Korean jade") – softer, lower RI
• Quartzite ("Jadeite quartz") – granular, no fibrous toughness
• Glass, plastic, dyed chalcedony – imitations

Gemological Identification

• Refractive index: Jadeite 1.66–1.68; Nephrite 1.60–1.63
• Specific gravity: Jadeite 3.33; Nephrite 2.95
• Spectroscope: Jadeite shows Cr lines (437, 467, 691 nm); Nephrite lacks
• Raman spectroscopy: Definitive mineral ID

Cultural Significance

• Nephrite: Traditional Chinese jade (Neolithic onward); Māori pounamu (greenstone)
• Jadeite: Introduced from Burma (Myanmar) 18th c.; now premier for high-end jewelry
• Value factors: Color (imperial green, lavender), translucency, texture, cut, size

"Jade" is a cultural/gemological category, not a single mineral. Always specify jadeite or nephrite for accurate description.