Lapis Lazuli

Lapis Lazuli

Lapis Lazuli is selected with uniform color and no cracks, fine texture and no gold stars, followed by no white gold, which means that gold stars are evenly distributed. If the content of pyrite is low, no gold stars will appear on the surface and will not affect the quality. However, if the color of Venus is black or dark, or if the calcite content is too much to form a large area of white spots on the surface, the value will be greatly reduced.

Lapis lazuli, turquoise and zircon are the same birthstones in December.

Lapis lazuli usually has two meanings.

First, it refers to alkaline aluminosilicate minerals. Chemical formula (Na,Ca)7~8(Al,Si)12(O,S)24[SO4,Cl2(OH)2]. The sodium is often partly replaced by potassium, and the sulfur part is replaced by sulfate, chlorine and selenium. Since the research on the mineral lapis lazuli has not yet been thoroughly studied, there are other different ways of writing its chemical formula, for example: (NaCa)8(AlSi04)6(SO4,cl,S)2, at this time the mineral is equiaxed crystal system, refraction Rate N=1.50, dark blue, blue-violet, sky blue, light blue or green-blue.

Second, it refers to a rock dominated by lapis lazuli minerals, a cryptocrystalline aggregate containing a small amount of impurities such as pyrite and calcite. The cleavage is not developed, the fracture is uneven, and the streaks are light blue. It emits orange spot light under long-wave ultraviolet light irradiation, and white fluorescence under short-wave ultraviolet light irradiation. Light red under the color filter. Glass luster to waxy luster, refractive index N=1.502~1.505, relative density 2.7~2.9. Lapis lazuli slowly releases hydrogen sulfide when it encounters hydrochloric acid.

Identification method

The granular structure of natural lapis lazuli can be seen under a magnifying glass, and often contains pyrite spots and white calcite clumps. [2] 

Lapis lazuli is generally blue, and its color is determined by the content of lapis lazuli minerals. Good lapis lazuli is dark blue and pure, with no cracks, fine texture, and no calcite impurities. It can be made into jewelry and so on. If there are white stone threads or white spots intertwined, the color density, purity and uniformity will be reduced, and the quality of jewelry will be reduced.

The texture of lapis lazuli should be dense, delicate, without cracks, and the pyrite should be evenly distributed like glittering stars, which is top-grade. The local distribution of pyrite in pieces will affect the texture of the lapis lazuli jade, and the more obvious the cracks, the lower the quality level.

Evaluation rating

The quality evaluation of lapis lazuli can be based on color, clarity, weight (lumpness) and other aspects. To

color

The color of lapis lazuli is determined by the content of the lapis lazuli mineral. If it contains more lapis lazuli minerals, the color is good, and vice versa. Because the lapis lazuli mineral is blue, the lapis lazuli jade is average. It is also blue, and the best blue tone is strong, pure and uniform. 

If the color is intertwined with white stone lines or white spots, the density, purity and uniformity of the color will be reduced, and the quality will be reduced.