Scheelite crystal properties and uses

What is Scheelite?

Scheelite is an important tungstate mineral with the chemical formula CaWO₄, which is mainly composed of calcium and tungsten. Scheelite is mainly formed under high temperature and high pressure environment, and is common in hydrothermal deposits and contact metamorphic belts. Its formation process involves magmatic activity, hydrothermal action, metamorphism and contact metamorphism, and it often coexists with minerals such as quartz and fluorite. These minerals usually appear in hydrothermal veins, veins, metamorphic belts and igneous rock areas. There are scheelite resources in many regions of the world, and its exploration and mining mainly use its fluorescence properties.

Characteristics of Scheelite Crystals

Scheelite crystals belong to the tetragonal system, and bipyramidal, plate-like and columnar forms are common. The surface of the crystal is usually smooth, and occasionally slender edges can be seen.

Scheelite crystals often have parallel plane structures, and the color is mostly white, and sometimes light green, light yellow, etc. The color change is mainly related to the impurities it contains.

Due to the anisotropy in the scheelite crystal, it has birefringence, has obvious optical effects under light conditions, and can have different refractive indices.

Scheelite emits blue fluorescence under ultraviolet light, which is one of the most iconic characteristics of scheelite, making it unique in mineralogy and the gem industry.

Scheelite crystals vary in size, ranging from a few millimeters to a few centimeters, and their transparency is average, usually translucent or opaque. Translucent scheelite crystals show beautiful color changes under sunlight.

Characteristics of Scheelite

Physical properties: Scheelite has a medium hardness of 4.5-5 and a relatively high density of about 6.1 g/cm³. Scheelite has a glassy to resinous luster, a translucent to opaque state, and is usually white, gray or light yellow.

Chemical properties: Scheelite has a chemical formula of CaWO₄, which is mainly composed of calcium, tungsten and oxygen. It can be soluble in acid, but it is difficult to dissolve in water.

Uses of Scheelite

Scheelite is the main raw material for extracting tungsten, and its uses are as follows:

Industrial use: Tungsten is used to make hard alloys, which can improve the hardness, wear resistance and heat resistance of steel, and is used to make high-speed cutting tools; it can also be used to make electronic components, such as filaments of light bulbs, targets of X-ray tubes, etc.;

Chemical use: Tungsten compounds are used as catalysts in chemical production, such as petroleum refining and chemical synthesis.

Scientific research use: As a typical tungstate mineral, scheelite has important value in mineralogical research.

Other uses: The fluorescent properties of scheelite make it useful in the manufacture of fluorescent materials. In addition, the high density of tungsten makes it suitable for radiation shielding materials, used in the medical and nuclear industries.

Scheelite beneficiation process

The scheelite beneficiation process generally includes crushing and grinding, gravity separation, flotation, magnetic separation, chemical separation, dehydration and drying, and tailings treatment. Through these steps, scheelite can be effectively separated and enriched to obtain high-grade concentrate.

Crushing and grinding: Use a jaw crusher or a cone crusher to crush the raw ore to a smaller particle size. The crushed ore is further ground by a ball mill to fully dissociate the minerals.

Gravity separation: Using the difference in mineral density, the scheelite and gangue minerals are separated by a shaking table. It is suitable for processing fine-grained ores and separating minerals by spiral water flow.

Flotation: Add collectors and frothers to make the bubbles attached to the scheelite particles float out. The roughing concentrate is repeatedly refined to improve the grade of scheelite. The roughing tailings are scavenged to recover the residual scheelite.

Magnetic separation: If it contains magnetic minerals, a weak magnetic separator is used to remove it.

Chemical ore dressing: For difficult-to-select ores, acid leaching or alkali leaching is used to extract tungsten. Tungsten is recovered from the leachate by chemical precipitation.

Dehydration and drying: Use a concentrator to concentrate the flotation concentrate. Remove the moisture in the concentrate through a filter. Use a dryer to dry the filtered concentrate for easy storage and transportation.

Tailings treatment: Recycle the valuable components in the tailings.

Author: Xingaonai
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