Brief introduction of lapis lazuli

Celestine is a crystal of chemical composition SrSO4 and belongs to the orthogonal (orthortic) crystal system of sulfate minerals. Celestite is mainly used in the manufacture of barium carbonate and the production of television tube glass. Its color is blue, green, yellow green, orange, light blue gray, etc., and sometimes it is colorless and transparent.

Forms a complete class with the barite, and is rich in strontium called celestite. It is often thick plate or columnar crystal, mostly dense block or plate-like, granular aggregate. Pure, colorless and transparent, some with light blue or blue-gray, white streaks, glass luster, transparent to translucent. The three sets of cleavage are complete and the angle is equal to or close to 90°. Mohs hardness of 3-3.5, specific gravity of 3.9-4.0. The flame is dark purple when burning celestite fragments.

The celestite formed by the deposition is associated with carbonate and gypsum, and the hydrothermal celestite is often produced by the vein. The Aojingshan lapis lazuli deposit in Fuyang, Jiangsu, China is the largest antimony deposit in Asia. Celestite is mainly used in the manufacture of barium carbonate and the production of television tube glass.

Chemical composition: SrSO4, strontium-containing ore; component Sr(SO4), containing Sr45%~47%, sometimes containing barium and calcium; (Sr, Ba)SO4. The Sr content is greater than Ba, and may contain elements such as Pb, Ca, and Fe.

Crystal system: orthorhombic system

Crystal habit: plate or column and plate crystal, orthorhombic double cone crystal, plate crystal. Incomplete crystals are rare, mostly aggregates, in the form of stalactites, tuberculosis, fibrous, fine-grained

Color: blue, green, yellow-green, orange or colorless; light blue-gray, sometimes colorless and transparent.

Gloss and transparency: glass luster, cleavage surface is pearl luster, transparent to translucent

Photometric: biaxial crystal, positive light

Refractive index: 1.619~1.637; birefringence 0.018

Polychromaticity: weak

Absorption spectrum: not obvious

Cleavage: The cleavage parallel bottom surface {001} is complete, the two groups are completely cleavage, and the parallel oblique column {210} is medium.

Mohs hardness: 3.0~3.5

Density: 3.97~4.0g/cm^3

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