HomeClassification of Jade
Jadeite-jade is a monoclinic mineral belonging to the pyroxene group with a chemical composition of NaAl(SiO3)2. Jadeitite is composed of interlocking grain structure. Jadeite together with one or two closely related pyroxenes: acmite [NaFe(SiO3)2], or diopside [CaMg(SiO3)2] forms a continuous isomorphic substitution series. Variations in the properties of jadeite depends on the proportions of each pyroxene present. For example, if diopside forms as part of the jadeite composition, then the material can be called diopside-jadeite. If an intermediate composition of acmite and jadeite is present, it is known as chloromelanite. This material appears blackish green to nearly black, due to the presence of a certain amount of iron.

Besides acmite and diopside, there are other pyroxenes like ureyite and aegerine as shown in the mineral association below.

In order to distinguish between the type of jadeite, an advanced method of identification such as thin-section work, X-ray diffraction and Energy Dispersive Spectroscopy. 

· Solid solution series – Kosmochlor (Ureyite) (NaCrSi2O6) - NaFeSi2O6 (Aegirine) - Jadeite (NaAlSi2O6).

NaCrSi2O6

 

 

 

 

 
 

Ureyite

 

 



50% 50%

 

           
   
 

Aegerine

   

Jadeite

 

 

 

 

 

 

NaFeSi2O50% NaAlSi2O6

Mol per cent

Further study by Dr. Win Htein and Daw Aye Myo Naing of Yangon University, Myanmar, using physical, optical and X-ray data suggests that jadeite could further be divided into pure jade (monomineralic) and impure jade (polymineralic) as shown below.

 

Monomineralic - Jadeite

(Pure jade) - Jadeite ± rutile/ilmenorutile

- Jadeite ± chromite / magnesiochromite ± rutile

 

Polymineralic - Jadeite + edenite + richterite ± chromite

(Impure jade) - Jadeite + kosmochlor ± ilmenorutile

- Jadeite + enstatite + tremolite

- Jadeite + tremolite + edenite + richerite + Kosmochlor ±

ilmenorutile

 

[Isomorphous – Applied to two compounds having the same, or nearly the same, crystal form and containing ions of approximately the same size or relative size. Solid Solution – Solid crystalline phases representing a mixture of two or more end-members and which may vary in composition within finite limits without the appearance of another phase.]

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