Sands and their diversity on Earth

 The article presents data about the mineral composition, color scale and shape of detrital grains of the sand collection assembled in diff erent parts of the Earth. This study led to conclusions about the formation, transportation and accumulation of sands in diff erent climatic and tectonic conditions. The studied samples represented sandy alluvial deposits of the shores of the Atlantic, Pacifi c, Indian oceans, rivers and streams of the Lena River basin, inland seas and lakes of Russia, as well as eolian deposits of the Sahara desert and tukulans sand dunes.

The purpose of the study was to clarify the composition of sands of diff erent genesis and conduct a comparative analysis to reveal the conditions for their formation. The analyzed material showed a wide variation in the color range of sands, a relationship with the mineral composition of primary rocks and transportation conditions. As a result of

the research, alluvial, marine monomictic, graywacke (basalt, calcareous), polymictic-greywacke, calcareous sands, eluvial-alluvial clayey sands with a large amount of plant residue were established for the fi rst time. According to the shape and degree of wear of detrital grains, the minerals and sands were divided into sediments of near and far transport. The range of transfer of clastic grains of minerals and rocks was confi rmed by their preservation during the diagenetic transformation of sands. In sandstones, fragments of unstable silicates were not observed; a small amount of rock fragments (carbonates, basalts, metamorphic rocks) was established.

Under platform conditions, in contrast to the alluvial sands of rivers, seas, oceans, chemical weathering prevailed over mechanical weathering in mountain sands, which is refl ected in the red color of the sand and the presence of clay and iron hydroxides in the composition of the sand.

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