Lapis Lazuli
 
Basic Information
 
- Chemical Composition: It is mainly composed of (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₁₋₂ and belongs to alkaline aluminum silicate minerals.
- Crystal Form: It belongs to the isometric system. Crystals are rare and usually in the shape of a rhombohedral dodecahedron. Aggregates are in dense massive or granular structures.
 
Appearance Features
 
- Color: Commonly seen in dark blue, violet-blue, sky blue, etc. Its unique blue color is determined by the absorption and reflection characteristics of light by its crystal structure.
- Luster and Transparency: It has a vitreous to greasy luster and is translucent to opaque.
- Hardness and Density: Its Mohs hardness is 5 - 5.5, and its relative density is 2.38 - 2.45.
 
Distribution of Origin
 
It is mainly distributed in countries such as Afghanistan, Russia, Chile, and Canada. Among them, the lapis lazuli produced in Afghanistan is of the highest quality.
 
Classification
 
It is divided into four categories: lapis lazuli, azure, hastite, and sugilite. The content of lapis lazuli minerals decreases in turn, while the content of impurities increases successively.
 
Historical and Cultural Significance
 
- Ancient Trade: As early as the 6th millennium BC, it was transported from Afghanistan to the Mesopotamia region and other places through long-distance trade. The "Lapis Lazuli Road" was an important trade route.
- Cultural Symbol: It was a precious jade in ancient India, Iran and other countries. In ancient Greece and Rome, it represented wealth. In ancient China, it was one of the "Seven Treasures of Buddhism".
 
Uses
 
- Jewelry and Handicrafts: It is used to make necklaces, bracelets, earrings and other ornaments as well as decorative items and carved artworks.
- Pigment: Ground into powder, it can be used as a high-quality blue pigment for painting murals and oil paintings.
 
Identification Methods
 
It is easy to be confused with sodalite, hauyne, etc. It can be distinguished by color, luster, hardness, density and professional testing. Common counterfeits include dyed marble, etc.

The following is an introduction to the fret pattern in the field of carving:
 
Basic Features
 
The fret pattern is composed of horizontal and vertical short lines that are folded and wound continuously, presenting a shape like the Chinese character "回" (hui). It has various forms such as single-unit, continuous, and variant forms. It can be arranged in a four-direction continuous pattern, or it can surround or be used as a partial embellishment on carved works.
 
Historical Origin
 
The fret pattern can be traced back to the Majiayao Culture in the Neolithic Age. It already appeared on the patterns of pottery at that time. During the Shang and Zhou Dynasties, the fret pattern was widely used as an auxiliary decorative pattern on bronze wares. In the Tang and Song Dynasties, it was commonly seen on porcelain. In the Ming and Qing Dynasties, it was widely used on various handicrafts such as jade, becoming a classic decorative pattern.
 
Cultural Connotations
 
The lines of the fret pattern are continuous and smooth, symbolizing endlessness and eternal good fortune, expressing people's longing and anticipation for a better life, and embodying the philosophical thought of cycle and recurrence in traditional Chinese culture, such as the alternation of the four seasons and the cycle of all things.
 
Common Types
 
- Square and Single-unit Type: With a central point, it extends outward to form a square, and then the independent single units are arranged intermittently in this way.
- Simplified and Combined Type: After reducing the strokes of the "口" (kou) character in the fret pattern, they are recombined.