Nephrite
Nephrite is one of the two varieties of jade, the other is jadeite and although similar in appearance, they have different chemical compositions. Nephrite is very tough, even tougher than jadeite, due to its interlocking structure of microscopically fine fibrous crystals.
However jadeite is the harder of the two varieties.
Nephrite is called 'greenstone' in New Zealand and is traditionally thought of as this colour, but it also occurs in other colours such as white, orange, bluish-grey and black. The stone is translucent to opaque and is cut into cabochons, inlays and ornamental objects.
Jade has a long history as a prized material; ancient artifacts made from jade include weaponry, armour, objects of adornment, utensils, religious and personal ornaments.
Major sources of nephrite include: Canada, Korea, Mexico, Myanmar, New Zealand, Russia (Siberia), Taiwan and USA (Wyoming).
Properties of the Gemstone and Additional Information
| Gemstone type: | A member of the jade group, a polycrystalline material.. |
| Crystal System: | Monoclinic |
| Chemical Composition: | Calcium magnesium iron silicate, Ca2(Mg,Fe)5(Si8O22(OH)2 |
| Colour: | Shades of green and other colours eg. white, black, bluish-grey, orange and brown |
| Lustre: | Greasy or vitreous |
| Pleochroism: | Absent |
| Dispersion: | None |
| Hardness: | 6 1/2 on the Mohs' scale |
| Toughness: | Excellent: due to an interlocking microscopic fibreous structure, it exceeds that of jadeite |
| Cleavage: | None |
| Density in gm/cc: | 2.8 to 3.1 |
| Double refraction: | Low |
| Refractive index: | 1.60 to 1.62 |
Common Treatments
Natural jade is described using an A to C classification to determine the type of treatment, if any, it may have received.
A jade is natural jade that has not been treated. It may be polished using a wax that does not contain dye.
B jade is natural jade that has been treated with fillers, usually polymers to fill fractures and surface depressions.
C jade is natural jade that has been dyed or stained.
When jade is treated with fillers that contain dye it is termed B+C jade.
Before treatment by fillers, the material may have been bleached to remove stains caused by other minerals.
Jade simulants are made from porous minerals dyed to jade colours. When compared to natural jade they are quite convincing.
Genuine gemstone materials that are similar in appearance to jade are also used as simulants. For example, aventurine quartz, hydrogrossular garnet and bowenite have all been used to simulate green quartz.