Nephrite

Specific Gravity: 2.96
Refractive Index: 1.61-1.63
Birefringence (DR): 0.027
Luster: Greasy to pearly
Crystal Structure: Monoclinic
Composition: Calcium magnesium iron silicate
Hardness: 6½

Nephrite is recognized as a separate type of jade since 1863. It is found as aggregates of fibrous amphibole crystals. These form an interlocking structure that is tougher than steel. Hence, nephrite is a popular stone for carving. Initially, it was used as a weapon. However, it has been used as an ornament lately. Nephrite colors vary from a dark green, iron-rich nephrite to a cream-colored, magnesium-rich variety.

Nephrite jade may be homogenous in color, banded, or botchy. It may be confused with bowenite serpentine. Moreover, it may be imitated by composite stones, or dyed to improve color. It is interesting to note the nephrite jade has been carved in China for centuries. The stone is tough enough to be worked into intricate carvings. China is still one of the main cutting centers.

Because of its great strength, nephrite has been used to make weapons. In fact, it was known as ‘axe stone’ at one time. It is common to fashion one side of the stone into a carving whereas keeping the other as is.

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Occurrence

Nephrite has been carved by the Chinese for more than 2,000 years. The raw material was probably imported first from Turkestan in Central Asia, and then Myanmar (Burma). Other localities include Pakistan, Siberia (dark green boulders, often with black spots), Russia (spinach-colored stones), and China.

Nephrite is also found in various rocks in the South and North islands of New Zealand. The pieces carved in the 17^th century include Maori clubs called meres. Other localities include Poland, Switzerland, Germany, Italy, Zimbabwe (dark green), Taiwan, Brazil, Mexico, Canada, the USA, and Australia (black nephrite).