Description

Natural Color Play Black Opal - PRODUCT ID:-> OPL/OPL2043 GEM TYPE:-> 100% Natural Black Opal SHAPE:-> Oval Cabochon WEIGHT:-> 2.34 Cts. SIZE:-> 11.50 x 9.30 mm QUANTITY:-> 1 Pieces (Nice Color Play) COLOR:-> Nice Peach Champagne CLARITY:-> VVS2 - Eye Clean LUSTER:-> Superior ORIGIN:=> Ethiopia TREATMENT:-> None HARDNESS:-> 5.50 Moh's Scale ColorPlay Opal Multi-Color Flashing On Gem, Fire Opal, Black Opal Healing with Opal ♥ Increases nobility ♥ Spiritual awareness ♥ Psychic abilities ♥ Inner peace and healing ♥ Healing of body, mind & soul ♥ Positive transformation ♥ Meditation ♥ Balance ♥ Relieves stress ♥ Communication Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. There are two broad classes of opal: precious and common. Precious opal displays play-of-color (iridescence), common opal does not.[4] Play-of-color is defined as "a pseudo chromatic optical effect resulting in flashes of colored light from certain minerals, as they are turned in white light."[5] The internal structure of precious opal causes it to diffract light, resulting in play-of-color. Depending on the conditions in which it formed, opal may be transparent, translucent, or opaque and the background color may be white, black, or nearly any color of the visual spectrum. Black opal is considered to be the rarest, whereas white, gray, and green are the most common. Precious opal shows a variable interplay of internal colors, and though it is a mineraloid, it has an internal structure. At microscopic scales, precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice. It was shown by J. V. Sanders in the mid-1960s[6][7] that these ordered silica spheres produce the internal colors by causing the interference and diffraction of light passing through the microstructure of the opal.[8] The regularity of the sizes and the packing of these spheres determines the quality of precious opal. Where the distance between the regularly packed planes of spheres is around half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The colors that are observed are determined by the spacing between the planes and the orientation of planes with respect to the incident light. The process can be described by Bragg's law of diffraction. Visible light cannot pass through large thicknesses of the opal. This is the basis of the optical band gap in a photonic crystal. The notion that opals are photonic crystals for visible light was expressed in 1995 by Vasily Astratov's group.[9] In addition, microfractures may be filled with secondary silica and form thin lamellae inside the opal during solidification. The term opalescence is commonly used to describe this unique and beautiful phenomenon, which in gemology is termed play of color. In gemology, opalescence is applied to the hazy-milky-turbid sheen of common or potch opal which does not show a play of color. Opalescence is a form of adularescence. For gemstone use, most opal is cut and polished to form a cabochon. "Solid" opal refers to polished stones consisting wholly of precious opal. Opals too thin to produce a "solid" may be combined with other materials to form attractive gems