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What is the actual color of opal?
Everyone knows the bright play of opal, shimmering with all the colors of the rainbow, or glowing blue or blue with green colors. But why are opals called white, black, brown ("chocolate", "coffee") or fire? It's all about the base color of the stone. The bright play of iridescent colors is not the opal's own color, but an optical effect caused by the decomposition of light falling on the stone. The structure of opal is similar to a diffraction grating, consisting of many opal globules, and the more uniform this structure, the brighter and more varied the play in the stone. The base color of the stone is determined by the amount and composition of impurities in the opal. These can be hydroxides of iron, manganese or aluminum, carbonaceous or other organic matter (bitumen). As a rule, the base colors of noble opals vary from white through shades of gray to black, and from colorless to yellow, red or brown, less often brown shades of colors are found. They also distinguish between crystal-opal, transparent or translucent type of opal, which can be colorless, white and "black".
В геммологической практике бывают весьма увлекательные случаи с диагностикой ювелирных вставок
Но помимо редкости цвета и высокой стоимости таких камней, многие розовые камни выделяются одной замечательной особенностью – они проявляют плеохроизм, то есть в зависимости от положения осмотра камня он может иметь дополнительные оттенки – оранжевый или пурпурный.
Currently, gemstones are produced by two fundamentally different technological methods - the High Pressure - High Temperature method (“HPHT”, High-pressure & High-temperature) and the Chemical Vapor Deposition (“CVD”, Chemical vapor deposition) method. The "HPHT" method is the most tested classical synthesis method, which can be used both carbon deposition on diamond from flux melts and catalytic reactions. In "CVD" synthesis, diamond growth occurs on a seed during carbon deposition mainly from a gaseous medium at relatively low temperatures and pressures.
Jewelry and precious stones are just such a category of goods, when buying which you need to pay attention to many criteria.
Sogdianite is a rather rare mineral and more often it can be found as a collection material (moreover, in systematic collections), and it is extremely rare in jewelry.