Ancient gem - Lapis Lazuli

The original name of lapis lazuli is LapisLazuli, from Latin LapisLazuli, which was called 璆琳, 金精, 瑾瑜, 青黛, etc. in ancient China. Buddhism is called 吠努离 or glaze, which is often used in the Buddhist world. Its handicrafts are called “green gold”, and ancient times it is called “Jinbi”, “point 黛” or “glazed”.

The lapis lazuli was developed and used by Central Asian countries as early as 6,000 years ago. China began in the Western Han Dynasty, when the names were "Lanchi", "Golden Dragonfly", "Points" and so on. Since the Ming and Qing Dynasties, the lapis lazuli "the color is like the sky", the sky is on, so the emperor of the Ming and Qing Dynasties re-emerged the golden stone.

Good lapis lazuli color is dark blue and pure, no cracks, fine texture, no calcite impurities. It does not contain Venus (pyrite) or has a very beautiful Venus. The world's famous lapis lazuli origins are Afghanistan, Chile, the former Soviet Union and Canada. But the first push for Afghanistan. The lapis lazuli produced in the country has a uniform dark blue to sky blue, and the fine crystal cryptocrystalline structure contains a trace of pyrite, which makes it shine under the sunlight. The lapis lazuli is called a “treasure” by the Arab Muslim countries.

Lapis gemological characteristics

The sodalite group mineral in the lapis lazuli framework silicate has a chemical formula of (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2. The crystalline aggregate has a dense block shape and a granular structure. The colors are dark blue, purple blue, sky blue, green blue, and the like. If it contains more calcite, it is striped white. When it contains pyrite, it will show yellow star point on the blue background, glass luster and waxy luster. The streak is light blue, translucent to opaque. The refractive index is about 1.50, the Mohs hardness is 5-6, and the specific proportion of lapis lazuli is 2.7-2.9. The cleavage is not developed, and the fracture is staggered. It emits orange spot light under long-wave ultraviolet light and emits green or white fluorescence under short-wave ultraviolet light. The color filter is light red and slowly dissolves in hydrochloric acid.

The cause and origin of lapis lazuli

The lapis lazuli is formed by contact metamorphism, mainly in silicate-magnesium skarn and calcareous skarn.

The lapis lazuli is mainly a semi-precious stone composed of a variety of minerals such as azure, sodalite, blue smectite, pyrite and calcite. The golden point-like substance on the lapis lazuli is actually pyrite. The white cloud-like structure is calcite. The ancient jewels in Egypt and the Middle East are often seen as jewels made of lapis lazuli, and even considered by the Egyptians to be a holy stone.

Due to the different proportions of the constituent minerals, the color and texture of lapis lazuli will be slightly different. The body blue of lapis lazuli varies in shades depending on the place of origin, mainly determined by the proportion of blue minerals and white calcite. The texture on it has a golden yellow spot formed by pyrite or a white grain formed by white calcite. In general, the body color of the superior lapis lazuli is moderate and saturated blue. At the same time, it is more popular with the golden spot on it.

Lapis lazuli origin

The main producing areas of lapis lazuli are Afghanistan, the United States, Mongolia, Myanmar, Chile, Canada, Pakistan, India and Angola. No lapis lazuli deposits have been found in mainland China.

The difference between lapis lazuli and similar jade

It is easy to be confused with lapis lazuli, such as sodalite, blue smectite and azurite. Counterfeit and substitutes posing as lapis lazuli are colored jasper, colored spinel, colored jade, imitation green gold, and dyed marble.

Similar jade features are as follows:

Sodalite (also known as soda stone), has a coarse crystalline structure, uniform color, hardness 5.5-6, specific gravity 2.15-2.35, refractive index 1.48-1.487, texture is not as uniform as lapis lazuli, orange and pink fluorescence.

Blue stellite, orange-red fluorescence, specific gravity 2.44-2.50, refractive index 1.496-1.504.

Azurite, small hardness, 3.5-4, refractive index 1.73-1.83, birefringence: 0.108, brittle, no large dense block.

Colored jasper (also known as Swiss green gold), artificially colored with pseudo-materials such as chalcedony or jasper, with a hardness of 6.5-7, a refractive index of 1.53-1.55, and a specific gravity of 2.6.

Colored spinel (also known as colored green gold), artificially colored with cobalt salt, has a high hardness of 8, and a refractive index of 1.71-1.73.

Coloring jade jade (also known as twilight green gold), light blue, can not see pyrite, strong grease gloss, hardness 4.8-5.5, refractive index 1.56-1.57, specific gravity 2.54-2.84.

It is imitation of green gold, made of glass, made of colored dark blue sulfur or glass. It can't see pyrite, glass luster, shell-like fracture, and brittleness. Dyed marble, the hardness is small, the knife is easy to inject, and the reaction with hydrochloric acid is obvious.

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