How to Identify Sheep Fat White Jade:
SHEEP FAT WHITE JADE is considered the highest quality of Hetian jade. It is known for its pure, bright white color, superior luster, and smooth texture. This type of jade is often described as "warm, firm, pure, and flawless," with a soft, gel-like appearance that gives it its name. One of the easiest ways to distinguish it from regular white jade is by observing it under a white fluorescent light. When exposed to this light, sheep fat white jade appears translucent with a soft, powdery glow.
Ordinary white jade, on the other hand, may appear translucent under a fluorescent light but lacks that powdery or milky effect. Another key difference is that even the whitest white jade will show a slight yellow tint under fluorescent light. If a piece shows any yellowish hue, it cannot be classified as true sheep fat white jade. True sheep fat jade meets strict criteria and is rare, often appearing subtle and unassuming at first glance. To fully qualify as sheep fat jade, it must meet five essential characteristics: pure texture, fine structure, good water clarity, white fat color, and heavy oiliness.
Pure Texture:
The mineral composition of sheep fat jade is predominantly tremolite, typically reaching up to 99% purity. This jade forms in the most perfect part of wall rock alteration, where granodiorite comes into contact with dolomite. The resulting contact metamorphism transforms the dolomite into dolomite marble, and later magmatic hydrothermal fluids move through the fissures of this marble to form tremolite.
The surrounding rocks undergo transformation into three distinct lithofacies: dolomite marble, tunnelized petrochemical dolomite marble, and metamorphic rock. Sheep fat jade is found within the tremolite rock facies. Its hardness ranges from 6 to 6.5, second only to jadeite, and it has exceptional toughness and wear resistance. The texture is dense, and its chemical stability is very high.
Fine Structure:
The tremolite crystals in sheep fat jade are microscopically crystallized and aggregated. Under an electron microscope or optical microscope, the length of tremolite fibers in the jade can be measured, ranging from 0.033 to 0.01 mm in length and 0.0006 to 0.001 mm in width. These tiny, fluffy, felt-like crystals intertwine to form a pile-like, felt-like, or interwoven structure. Under polarized light, these crystal aggregates do not exhibit uniform extinction at the same angle.
Water Head:
"Water head" and "spirit land" refer to the transparency of jade. In tremolite jade, the standard thickness is usually around 2 mm. At this thickness, white jade is generally translucent to opaque. However, sheep fat white jade is translucent, showing excellent clarity and depth.
Color: Sheep Fat White:
The white color of sheep fat jade is not purely white, but rather a white with an oily sheen. Some pieces may show a slight yellow tone, while others might reveal a faint grayish undertone if the texture is not ideal.
Oily Weight:
When held in the palm, sheep fat jade naturally develops an oily feel on its surface. This sensation is also present in some high-quality Hetian white jades. When the jade is submerged in water, the dripping water should not stick to it, indicating good oiliness and weight. This quality is also referred to as “cotton,†which relates to the jade’s toughness and overall feel.
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