Nephrite
Nephrite is a variety of the metamorphic rock jade. Chemically, it is a calcium magnesium silicate with the formula Ca2(Mg,Fe)5Si8O22(OH)2. It is one of two distinct minerals recognized as jade, the other being jadeite.
Characteristics:
- Color: Nephrite jade typically ranges in color from dark green to creamy white, but can also be found in shades of brown, black, and grey. The color is primarily due to the presence of iron.
- Luster: Nephrite exhibits a greasy to vitreous luster.
- Hardness: Nephrite has a hardness of 6.0 to 6.5 on the Mohs scale.
- Tenacity: It is extremely tough, due to its interlocking fibrous structure, making it resistant to breakage. This toughness is a key characteristic differentiating it and contributing to its historical uses.
- Crystal System: Monoclinic.
- Fracture: Splintery.
- Specific Gravity: 2.90 to 3.03.
Occurrence:
Nephrite forms in metamorphic rocks, particularly serpentinites and amphibolites. Notable sources include:
- Canada (British Columbia)
- China
- New Zealand
- Russia
- Australia
- Taiwan
- United States (Wyoming, Alaska)
Uses:
Nephrite has been valued for thousands of years for its beauty, durability, and perceived spiritual properties. It has been used to create:
- Tools and Weapons: Historically, nephrite was used for axes, adzes, knives, and other tools and weapons due to its toughness.
- Ornaments and Jewelry: It is commonly carved into beads, pendants, bangles, and other decorative items.
- Sculptures: Nephrite is a popular material for carvings and sculptures, particularly in Chinese art.
- Ceremonial Objects: In many cultures, nephrite has been used to create ritual objects and artifacts.
Distinction from Jadeite:
While both nephrite and jadeite are called "jade," they are chemically and structurally distinct. Jadeite is a sodium aluminum silicate and is generally harder and more vitreous than nephrite. Jadeite also typically occurs in brighter, more vibrant colors, including various shades of green, lavender, and red.
Cultural Significance:
Nephrite holds significant cultural importance in many societies, particularly in China, where it has been revered for millennia. It is associated with qualities such as purity, longevity, wisdom, and harmony. In Māori culture of New Zealand, nephrite (known as pounamu) is highly prized and considered a taonga (treasure).