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, snow-white color and exceptional luster and texture. This type of jade is characterized by its warm, smooth feel, purity, and flawless appearance—resembling gelatin in texture, which gives it its name. One of the simplest ways to distinguish it from regular white jade is by observing it under a white fluorescent light. When exposed to such light, sheep fat white jade appears as a pure white, translucent piece with a soft, powdery glow.
Ordinary white jade may appear translucent under fluorescent light, but it lacks that powdery sensation. The key difference is that while most white jade looks very white to the naked eye, it often shows a slight yellowish tint under fluorescent lighting. Therefore, if a piece shows even a hint of yellow under such light, it cannot be classified as sheep fat white jade. True sheep fat jade, which meets strict standards, is usually subtle and not overly flashy. To identify genuine sheep fat jade, five key characteristics must be met: pure texture, fine structure, good water clarity, a white-fat color, and a heavy, oily feel.
Pure Texture:
The mineral content of tremolite in sheep fat jade is typically over 99%. This jade forms in the most perfect parts of wall rock alteration. When granodiorite comes into contact with dolomite, contact metamorphic rocks are created, turning dolomite into marble. Later, hydrothermal fluids move through these tectonic fissures, transforming into tremolite. Over time, surrounding rocks undergo changes, forming three types of 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 the highest toughness and wear resistance among all jades. Its dense texture and stable chemical properties make it highly valued.
Fine Structure:
The tremolite in sheep fat jade is microscopically crystallized and aggregated. Under an electron or optical microscope, the length of the tremolite fibers can be measured at 0.033 to 0.01 mm in length and 0.0006 to 0.001 mm in width. These microscopic, fluffy, felt-like crystals form a complex network of pile-like, felt-like, and interwoven structures. Under polarized light, they do not show uniform extinction, which helps in identification.
Water Head:
“Water head†refers to the transparency of the jade. In tremolite jade, the standard thickness is about 2mm. Most white jade appears translucent to opaque at this thickness, but sheep fat white jade remains translucent, showing high clarity.
White-Fat Color:
The “white fat†of sheep fat jade is not purely white. It has a soft, oily sheen. Some pieces may show a faint yellow tone, while others might reveal a slight grayish hue if the texture is poor. However, the overall appearance is still rich and luxurious.
Oily Weight:
When held in the hand, sheep fat jade naturally feels oily and smooth. This sensation is also seen in some fine Hetian white jade. When submerged in water, the surface of the jade does not stick to the water, reinforcing its oily, heavy, and rich texture. This characteristic is often referred to as "cotton," indicating its strength and resilience.
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