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50 shades of grey
Over the past few years, there has been an increased demand for pastel-colored stones in the global jewelry market. One of these stones is the gray spinel. Its popularity increased especially sharply after the release of the film "50 Shades of Gray".
Indeed, gray spinel has a great variety of shades. It can be of different saturation - from light gray to dark graphite. Also, in addition to gray, spinel is characterized by the presence of an additional shade - purple, blue or blue-green.
The gray color of spinel is associated with the presence of different-valence iron ions in various structural coordinations, as well as with additional impurities of manganese and titanium, less often zinc and nickel. Sometimes, for gray spinel, red fluorescence is observed, which is due to the impurity of chromium.
The main sources of spinel are genetically related to metasomatic and metamorphic rocks depleted in silica and enriched in an aluminum-magnesian component, however, gem-quality stones are most often mined from placer deposits of various types.
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.