How to judge the quality of brown corundum?

To judge the quality of brown corundum , it is necessary to conduct a systematic evaluation based on the appearance characteristics, physical properties, chemical composition and industry specifications. The specific standards are as follows:

Appearance characteristics

Color High-quality characteristics: dark brown-red, dark brown or brown-brown, uniform color, good light transmittance (transparent or slightly blue when observed in the sun) Poor-quality characteristics: abnormally bright, black, rose red, may contain impurities or excessive iron content.

Physical property test

Hardness test Use a hardness tester (Vickers or Rockwell) to test, and the compressive strength must meet the standard; simple test: hand-press the particles on white paper, and easy to break indicates insufficient hardness. Impurity adsorption Use a magnet to adsorb the sample. The less magnetic material, the higher the purity of the alumina and the lower the impurity content (such as iron). Wear resistance and ash content Wear resistance can be compared with standard samples by a wear tester; ash content test: no white floating objects on the water surface after soaking in clean water are preferred.

Chemical composition analysis

Alumina (Al₂O₃) content First-grade: Al₂O₃ ≥ 94-95% (some high-purity products ≥ 96%); Second-grade: about 90-80%; Third-grade: lower content Impurities such as iron (Fe) and silicon (Si) must be strictly controlled at a low level.

Reasonable price

High-quality products are expensive (reference: market price of first-grade products is 4500-5500 yuan/ton), and low-priced products may be mixed with secondary raw materials.Pit avoidance guide

Beware of low-price traps: Products with black, opaque or rose red colors are mostly inferior products with high loss rates. Verify Purity: Manufacturers are required to provide a third-party ingredient testing report, with a focus on checking Al₂O₃ and impurity content.