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This heading covers natural mica, further worked than merely rifted and trimmed (e.g., cut to shape), and also products consisting of agglomerated (bonded) mica or pulped (reconstituted) mica, and articles made from any of these materials.
Thin sheets and splittings obtained by merely rifting and trimming mica books as mined fall in heading 25.25.
The heading covers products obtained by cutting such sheets and splittings. Since they are obtained with a die-punch, their edges are clean cut.
Natural mica is often used as such in the form of sheets or splittings. However, since the small size of the crystals and their poor flexibility, high cost, etc., render natural mica unsuitable for many uses, it is frequently replaced by agglomerated (built-up) mica (e.g., micanite, micafolium), which is obtained by bonding mica splittings one above the other or side by side using shellac, natural resins, plastics, asphalt, etc. Agglomerated mica is made in sheet, plate or strip form, in all thicknesses, often with a fairly large surface area; the sheets, etc., are generally backed on one or (usually) both surfaces with textile fabric, glass fibre fabric, paper or asbestos.
Thin sheets of mica may also be obtained, without employing a binding agent, by submitting powdered and pulped mica waste to a thermal, chemical and mechanical process similar to that used for making paper (reconstituted mica).
These thin sheets are then mounted on to a paper or textile backing using a flexible bonding material; alternatively, they may be used for the manufacture of plates and strip of specified thicknesses by superimposing several thin sheets and bonding them with an organic binder.
The heading covers sheets, strips and rolls in the length; pieces cut to shape for special uses in the form of rectangles (including squares), discs, etc.; moulded articles such as tubes, conduits, etc. All these goods may be coloured in the mass, painted, drilled, milled or otherwise worked.
Owing to its high resistance to heat and its relative translucency, mica is used, inter alia, for the manufacture of windows for ovens, stoves, furnaces, etc., of unbreakable lamp "glasses", and of "glasses" for goggles, etc. But mica is mainly used in the electrical industry because of its excellent dielectric properties (in the manufacture of motors, generators, transformers, capacitors, resistors, etc.). It should, however, be noted that mica insulators and other mica insulating parts of electrical apparatus, even unmounted, fall in headings 85.46 to 85.48, and that mica dielectric condensers (capacitors) fall in heading 85.32.This heading further excludes : (a) Powdered mica and mica waste (heading 25.25). (b) Paper or paperboard coated with mica powder (heading 48.10, or 48.14), and woven fabrics coated with mica powder (heading 59.07). These products should not be confused with agglomerated or reconstituted mica as described above. (c) Expanded vermiculite (heading 68.06) (see relative Explanatory Note). (d) Mica goggles and eyepieces therefor (heading 90.04). (e) Mica in the form of Christmas tree decorations (heading 95.05).
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