Agglomerated or reconstituted mica under 681410 is manufactured by bonding mica flakes or splittings with a binder to form uniform plates, sheets, or strips — an engineered product with consistent properties. Subheading 681490 covers naturally split mica, mica on paper or other supports, and other worked mica articles that have not been reconstituted from flakes. The manufacturing process — reconstituted versus naturally worked — is the key distinction.

Worked mica articles are primarily used in electrical and electronics applications — as insulating components in motors, generators, capacitors, and heating elements — because of mica's combination of high dielectric strength and thermal stability. Specialty industrial uses include furnace windows and high-temperature gaskets. The specific end-use application often determines whether a buyer needs reconstituted sheet mica (681410) or a shaped natural mica article (681490).