NOVELTY - The polygon shaped crucible comprises an opening, and a metal coating layer including an oxide, hydroxide, nitride, carbide, oxynitride, oxycarbide, carbonitride or oxycarbonitride on its inner and/or outer surfaces. The polygon has four sides. The crucible has a density of 2.15 mm and a depth of 1.5 mm, and is made of fused silica arc. The opening has an area of greater than 0.9 m2.    USE - The polygon shaped crucible is useful: for calcination of powder such as alumina, phosphorescent powder or luminescent powder; for melting rare earth metals such as monocrystalline or multicrystalline silicon (claimed); in industrial applications such as semiconductor and solar cell; for refining precious metals such as gold, silver and platinum; for manufacturing synthetic gemstone; for melting and refining alloys such as powders, marbles and granules; for metallization of pieces by evaporation; for melting and/or crystallization of metal ingots by solidification processes or zone-melting silicon or other metals; for casting glasses; for the calcination or heating of acids or chemical mixed with acids such as hydrofluoric acid and hydrochloric acid; as a tank for washing, cleaning or etching wafers in the semiconductor industry; for heat treatment of pieces; for melting superalloys for turbine blades in the framework of their hot molding; for making preforms and transparent boxes for airwave applications of electromagnetic waves of radio frequencies or radio-transmissions; and as reactors for wafer processing.    ADVANTAGE - The thin crucible can be economically fabricated with excellent surface quality, enhanced thermal insulation property, high capacity, long lifespan and improved productivity and without any deformation.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a process for fabrication of a polygon shaped crucible.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a mold with rectangular opening.    Back wall (10)    Holes (11)    Side walls. (12, 13, 14, 15)