Jade Glossary
Essential terminology for understanding jade materials, treatments, testing methods, trade standards, and geological formation.
Definition
A trade name covering two principal materials: nephrite and jadeite-jade. In gemmology, 'jade' is not one mineral — it is a commercial term for tough polycrystalline aggregates of specific mineral compositions.
Context
The LMHC standardised definition covers aggregates primarily composed of jadeite, omphacite, kosmochlor, or nephrite. Always demand species identification (not just 'jade') when purchasing.
Definition
A sodium-aluminium pyroxene mineral (NaAlSi₂O₆) that forms polycrystalline aggregates. The more valuable of the two jade minerals, prized for its vivid colours and translucency.
Context
Jadeite is primarily sourced from Myanmar and Guatemala. Fine jadeite (especially Imperial Green) can be extremely valuable. RI typically ~1.65-1.67, SG ~3.25-3.40.
Definition
A calcium-magnesium-iron amphibole rock composed of tremolite-actinolite. The tougher (but generally less valuable) of the two jade minerals.
Context
Nephrite occurs worldwide — Canada, China, Russia, New Zealand, and others. The most prized variety is Hetian 'mutton fat' white jade. RI typically ~1.60-1.63, SG ~2.90-3.02.
Definition
A regulated term (particularly in Hong Kong) for granular-to-fibrous polycrystalline aggregates composed solely or principally of jadeite, omphacite, and/or kosmochlor.
Context
The Hong Kong consumer-protection standard defines 'natural' Fei Cui as not subjected to treatment altering crystalline structure or original colour. This term is widely used in Asian jade trade and laboratory reports.
Definition
A sodic-calcic pyroxene mineral that can form jade-like aggregates. Often classified under Fei Cui alongside jadeite.
Context
Critical identification challenge: GIA documented cases where stones tested as jadeite by classic methods (RI ~1.66) but were confirmed as omphacite by Raman spectroscopy. RI typically ~1.67-1.68.
Definition
A sodium-chromium pyroxene (NaCrSi₂O₆) that can form jade aggregates, typically dark green to black. Also known as ureyite.
Context
Included in the Fei Cui classification. RI typically higher (~1.68-1.72). Relatively rare compared to jadeite and omphacite.
Definition
Natural, untreated jade that has only been cut, polished, and may have received a thin traditional wax surface coating. No chemical bleaching, dyeing, or polymer impregnation.
Context
The only investment-grade jade. LMHC wording: 'No indications of impregnation.' Always require a laboratory certificate confirming Type A status for significant purchases.
Definition
Jade that has been chemically bleached to remove staining, then impregnated with polymer resin to fill resulting voids and improve appearance.
Context
The most commercially significant jade treatment. Detectable by FTIR (~2900 cm⁻¹ polymer absorption). Polymer degrades over 5-10 years — yellowing, cloudiness, or cracking may occur.
Definition
Jade that has been dyed — coloured agents introduced into fractures and grain boundaries to enhance or change colour.
Context
Detectable by colour concentrations along fractures under magnification, and by broad dye-related absorption bands in visible spectroscopy (vs natural Cr/Fe sharp lines).
Definition
Jade that has been bleached, polymer-impregnated, AND dyed. The most heavily treated category, combining all treatment risks.
Context
Shows both polymer signatures (FTIR) and dye evidence (spectroscopy/magnification). Poorest durability and lowest value. Selling as natural constitutes fraud.
Definition
A measure of how much light bends when entering a material. Measured using a gemmological refractometer. One of the most diagnostic classic tests for jade identification.
Context
Key ranges: Jadeite ~1.65-1.67, Omphacite ~1.67-1.68, Kosmochlor ~1.68-1.72, Nephrite ~1.60-1.63. Borderline results need lab confirmation due to jade heterogeneity.
Definition
The ratio of a material's density to that of water. Measured by hydrostatic weighing: SG = Weight in air / (Weight in air - Weight in water).
Context
Jadeite SG typically 3.25-3.40; nephrite 2.90-3.02. SG below ~3.32 in supposed jadeite may suggest polymer impregnation, but overlaps exist with untreated material.
Definition
A laboratory technique that measures infrared absorption patterns. The definitive method for detecting polymer impregnation in jade.
Context
Polymer impregnation produces strong absorption around ~2900 cm⁻¹ (C-H stretching). Also provides mineral fingerprints for identification. Considered the gold standard for jade treatment detection.
Definition
A laboratory technique that identifies minerals at grain scale by measuring scattered laser light. Can resolve spot sizes as small as ~1-3 μm.
Context
Critical for separating jadeite from omphacite — a distinction that classic tests (RI/SG) cannot always make. Uses spectral databases (e.g., RRUFF) for matching.
Definition
The most prized jadeite colour: a vivid, saturated, evenly distributed emerald green. Named for its association with Chinese imperial jade.
Context
Imperial Green jadeite commands the highest prices in the jade market — comparable to top-grade diamonds per carat. Must be combined with high translucency and fine texture for top value.
Definition
A Māori general term for South Island greenstone, encompassing nephrite, bowenite, and serpentinite found in New Zealand.
Context
Legally protected under the Ngāi Tahu Claims Settlement Act. Holds deep cultural significance as taonga (treasure). Raw pounamu export is restricted.
Definition
Nephrite jade from the Hotan/Khotan region of Xinjiang, China. The classical Chinese jade, prized for over 7,000 years.
Context
The most valued variety is 'mutton fat' (yang zhi yu) white jade — warm, translucent white with greasy lustre. River-tumbled 'seed jade' commands extreme premiums.
Definition
A material that resembles jade in appearance but has a completely different mineral composition. Not the same as treated jade.
Context
Common jade simulants: serpentine/bowenite, aventurine quartz, prehnite, pectolite, talc/steatite, idocrase, glass. GIA notes jade has more simulants than most gems.
Definition
A geological process where rock composition is changed by fluids. The primary mechanism for both nephrite and jadeitite formation.
Context
Nephrite forms by Ca- and Si-rich fluid metasomatism along serpentinite contacts. Jadeitite forms from Na-Al-Si rich fluids in HP/LT subduction settings.
Definition
A rock composed of serpentine-group minerals, commonly formed by hydration of mantle peridotite. The host rock for both nephrite and jadeitite deposits.
Context
Both jade types form in association with serpentinite. Serpentinite itself (and its variety bowenite) is also a common jade simulant — always verify identity.
Definition
Laboratory Manual Harmonisation Committee — an international body that standardises gemmological nomenclature and report wording across major gem laboratories.
Context
LMHC Information Sheet #11 defines jade, Fei Cui, and standardised treatment terminology used in lab reports worldwide. The 'house style' reference for jade nomenclature.
Definition
The World Jewellery Confederation — the international body representing the jewellery trade. Publishes the CIBJO Blue Books that define trade practice standards.
Context
The CIBJO Gemstone Book frames proper nomenclature and declaration of all known facts as foundations for consumer confidence and market stability.