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How the stars light up
In recent decades, the practice of creating the effect of asterism in corundums and spinels by diffusion treatment with saturation of the near-surface layer of the stone with titanium oxide, which crystallizes, forms accumulations of rutile inclusions, has been widespread. Regularly oriented rutile crystals, scattering the light incident on them, cause the iridescence effect in the form of asterism. In an earlier time, when there was no technology for surface diffusion saturation of stones with titanium oxide, there were some tricks. So, under the translucent stones with a weakly manifested asterism effect, a mirror substrate was brought up, reflecting light and causing, in addition to epiasterism (effect in reflected light) and diasterism (effect in transmitted light), which made the star more distinct. Sometimes doublets of cabochons were made with a layer capable of reflecting light and thus enhancing the asterism of the stone. True, for opaque and semi-translucent stones such a scheme was useless, and translucent stones had to be quite thin.
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.