On the method of determining minerals by scratch line and chemical reactions
Abstract
One of the diagnostic features by which the color of a mineral in powder is established is a scratch obtained on an unglazed porcelain plate (biscuit). The mineral scratch can also be used for chemical testing using the method of grinding with a solid chemical substance. It is also important to test the mineral scratch for decomposition in acids and alkalis. In the mineralogical practice of the Leningrad Mining Institute, the determination of minerals by the method of grinding a slcratch and chemical reactions on the mineral scratch is widely used. In macroscopic diagnostics of minerals, three methods are distinguished: 1) visual observation with the naked eye by the appearance of the mineral, i.e. the morphology and optical properties (color, luster, transparency and opacity of mineral individuals) are established; 2) visual determination with testing of the mechanical properties of minerals - hardness when scratched, brittleness when crushed, cleavage and fracture when splitting, the ability to be forged when flattened and obtaining a scratch on a porcelain plate; 3) chemical tests of the mineral or its scratch. Simultaneous use of these three methods allows for rapid diagnostics of minerals. The methods are applied in the specified sequence. Comparison of the color and luster of the scratch with the color and luster of the mineral helps in identifying the mineral. The proposed work provides a definition of those minerals that give a characteristic decomposition when dissolving or grinding the scratch, and minerals that are easily identified by film reactions. Diagnostics of minerals by scratch line and chemical reactions is given by classes, and within a class, minerals are arranged alphabetically.
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