Talc is a phyllosilicate mineral, a hydrated magnesium silicate. Pure natural talc is rare, and most of it is accompanied by other mineral impurities. Common associated minerals include chlorite, serpentine, dolomite, tremolite, and calcite. Talc is usually white, light green, slightly pinkish, or light gray in color. The more impurities it contains, the darker the color, ranging from dark gray to black. The talc mineral often appears in foliated, fibrous, or dense block forms, with a pearly or greasy luster. Its Mohs hardness is 1, and its density is about 2.7 g/cm³. Talc has a slippery feel and exhibits a significant thermal effect when heated. It loses adsorbed water between 120-200°C, and at 600°C, it loses part of its structural water. All structural water is expelled at around 1050°C.
Key Features
- Electrical insulation
Talc itself is not conductive. When talc mineral does not contain conductive minerals such as siderite, pyrite, and magnetite, its insulation is good. Talc porcelain made from talc has high insulation. When the temperature rises, the dielectric loss of block talc porcelain is much lower and slower than that of ordinary electric porcelain. - Heat resistance
Talc is both heat-resistant and non-conductive, with a refractoriness of up to 1490~1510℃. After calcination, the mechanical strength and hardness of talc increase, but the shrinkage rate is very low and the expansion rate is very small. It is a high-temperature resistant mineral material. - Chemical stability
Talc generally does not work with strong acids and strong alkalis. - Oil absorption and hiding power
Talc powder has a strong adsorption capacity for impurities in pigments, greases, agents, and solutions. Ultrafine talc powder, due to its good dispersibility and large surface area, covers a large area when applied on the surface of an object. It can form a uniform fireproof and weathering-resistant film. - Lubricity
Talc is soft and greasy, and is an excellent lubricating material. - Hardness variability
Talc is gradually heated to 1100℃, and then slowly cooled after about two hours. The appearance remains unchanged but the hardness increases. This is mainly because the talc has been transformed into orthoenstatite. - Machinability
The machinability is good. Talc fragments or talc powder are added with adhesives, and the semi-dry pressing method, wet pressing method, extrusion method or plastic method are used for processing and molding, and the product performance remains unchanged.
Main Application
- Industrial Uses: Talc powder is widely used in industry. It can be used as a filler and control agent in the paper industry to improve the performance of paper. In the plastic and rubber industries, talc can be used as a filler to improve the stability, strength and processing performance of products. In addition, talc can also be used in paint coatings, textile filling and whitening.
- Pharmaceutical Uses: In the pharmaceutical field, talc has the effects of clearing heat and dampness, relieving summer heat, and can be used to treat related symptoms caused by heatstroke. It can also be used as an astringent to treat skin diseases such as eczema and eczema. Talc is also used in pharmaceutical tablets, sugar coatings, prickly heat powder and traditional Chinese herb prescriptions.
- Building Materials: The application of talc in building materials includes the manufacture of high-frequency porcelain, radio porcelain, various industrial ceramics, building ceramics, daily ceramics and ceramic glazes.
- Cosmetics: Talc is a high-quality filler in the cosmetics industry. It has a high silicon content and can enhance the sunscreen and infrared resistance of cosmetics.
Selection Method
The selection methods for talc include flotation, hand selection, magnetic separation, electrostatic separation, photoelectric separation, and selective crushing and screening.
- Flotation Method
Commonly used collectors for talc flotation are kerosene and flotation oil as foaming agents. Methyl isobutyl carbinol produces brittle foam, making it easy to obtain high-quality fine powder. The flotation process requires only one roughing and sweeping selection, followed by 3-4 fine selections to obtain concentrate. However, talc concentrate has a fine particle size and is difficult to dehydrate. - Hand Selection Method
Talc has good slipperiness. The higher the grade, the better the slipperiness. Therefore, talc can be separated from other gangue minerals by hand selection. In China, most talc mines use hand selection to produce high-grade talc blocks. - Magnetic Separation Method
After flotation, some iron minerals may remain in the talc. To ensure purity, iron content is reduced by wet magnetic separation. This ensures the accuracy of the finished product. - Electrostatic Ore Dressing
Talc contains minerals like magnesite, magnetite, pyrrhotite, and tremolite, with an embedded particle size of about 0.5mm. In an electrostatic field, talc carries a negative charge, magnesite a positive charge, and magnetite and pyrrhotite are good conductors. This allows easy separation of these minerals. - Photoelectric Selection
Photoelectric selection sorts talc based on the different optical properties of talc and impurity minerals. The sorter includes an ore bin, feeder, belt conveyor, radiation source, detector, electronic control circuit, and actuator. It can also pick purer talc using its characteristic of emitting white fluorescence under ultraviolet light. - Selective Crushing and Screening
Talc and gangue minerals have different crushing characteristics. Impact crushing and alternating rectangular and square screens can separate most of the associated quartz and more than half of the carbonate minerals.
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