Ашарит

Description

Asharite is a hydrated magnesium borate with the composition 2MgO·B2O3·H2O, also known in mineralogy as szaibelite. The natural mineral is white in color and forms continuous clusters and veins, often intergrown with boronite. It belongs to endogenous borate ores and occurs in serpentinite massifs and salt-bearing sedimentary strata.

Basic Attributes

• CAS No: 12447-04-0
• Chemical formula: Mg2B2O3 H2O (2MgO B2O3 H2O)
• Substance class: inorganic salt, magnesium borate
• Synonym: szaibelite

Geological origin

Asharite is formed in endogenous deposits of borate ores and in salt-bearing sedimentary strata, and forms large accumulations in halogen members. Characteristic of serpentinite deposits. Mineralogical studies have shown the identity of asharite, camzellite and beta-asharite with the mineral szaibelite - all three names describe the same hydrated magnesium borate.

Scope of application

Asharite is one of the main sources of boron raw materials in China and Russia, along with colemanite. It is distinguished from colemanite by its low solubility in water, which determines the choice of processing technology.

• production of boric acid by the sulfuric acid method: when processing low-grade asharite, a recovery rate of boric acid of 71.06% and kieserite (magnesium sulfate) of 45.03% was achieved
• obtaining boric acid by decomposition of boromagnesium ore with sulfur dioxide
• extraction of magnesium by vacuum thermal reduction with aluminum powder, while boron is retained in the solid residue and used as a raw material for the production of alkali-free glass fiber
• extraction of magnesium by reduction with calcium carbide using the vacuum thermal reaction method

Chemical processing

To obtain boric acid, the ore is treated with sulfuric acid when heated, the borate goes into solution, and the insoluble residue is separated by filtration. A by-product of sulfuric acid processing is kieserite (magnesium sulfate), suitable for further use. An alternative scheme is decomposition with sulfur dioxide to produce boric acid without the formation of sulfate waste. When extracting magnesium, the ore is reduced with aluminum powder or calcium carbide in a vacuum at elevated temperature; the metallic magnesium evaporates and condenses, and the boron remains in the cinder in a form suitable for the glass industry.

Difference from colemanite

Colemanite is a water-soluble calcium borate and is processed by water leaching. Asharite is practically insoluble in water, so the processing scheme is based on acidic decomposition - with sulfuric acid or sulfur dioxide. The choice of reagent is determined by the grade of the ore: for low-grade raw materials, the sulfuric acid method with the associated production of kieserite is preferable; for purer batches, the method with sulfur dioxide, which does not produce sulfate waste, is preferable.

Storage and transportation

As a mineral raw material, asharite is stored and transported in bulk or in bags, in dry, covered conditions, without special temperature requirements. The material is non-hygroscopic and shelf stable due to its low solubility in water. Data on UN transport codes and hazard class for this mineral are not published in open sources - asharite is not classified as a dangerous cargo.