Macrocrystalline talc

Talc products are also characterized by their crystallinity or relative platiness. Mycrocrystalline talc products typical of Montana and AustraUa tend to have very fine natural grain sizes and thus are ea sily milled to very fine products of higher surface area (10—20 m /g). Macrocrystalline talc ores... 

Fig. 5. Scanning electron microscope photograph of macrocrystalline talc at xlOOO.

The talc/magnesite variety of ores are derived from serpentinite hosts and are typically found in Vermont, Quebec, and Finland. This type of ore is macrocrystalline in nature and composed of approximately 45-65% talc by weight, with the remainder of the ore made up of magnesite (magnesium carbonate). In some low-cost applications, such as automotive underhood, these ores are coarsely ground and used as is. These ores are also frequently beneficiated to 93-99 wt% talc by flotation. Because talc is hydrophobic, it is easy to float with surfactants. The talc floats on an aqueous bubble, whereas the co-mineral impurities sink in the water phase. 

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