themineralandgemnephilim:OpalVirgin Valley, NevadaOpal in its self is an amorphous, without a crysta
themineralandgemnephilim:OpalVirgin Valley, NevadaOpal in its self is an amorphous, without a crystalline structure, and without definite chemical composition. Therefore it is a mineraloid rather than a mineral. Opal gets its unique color due to a play-of-color are made up of microscopic spheres of silica arranged in a certain order. These spheres act as a diffraction grating. As the light passes through it is divided into the colors of the spectrum. The size of the spheres and their placement determine the color and quality of diffracted light.Composition: Hydrous silicon dioxide The water can range from 3% to 21% of the total weight but is usually between 6% to 10%.Chemical Formula: SiO2 · nH2OStreak: WhiteHardness: 4.5 - 6.5Luster: Usually vitreous, but may also be pearly, waxy, or resinous.Cleavage: NoneFracture: Conchoidal -- source link
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