The black sand is black kaolin, and kaolin is a common and very important clay mineral in nature. It is formed by weathering of the feldspar or other closyl minerals in the pyroclite and metamorphic rocks in the acid medium lacking alkali metal and alkaline earth metal.
The minerals in kaolin in nature are mainly composed of clay minerals and non clay minerals. Clay minerals include kaolinite minerals and a small amount of montmorillonite, mica and chlorite; non clay minerals include feldspar, quartz and enrolling hydrates, and some iron minerals such as hematite, siderite, limonite, titanium minerals such as Jin Hongshi and organic matter such as plant fibers. Clay minerals are the main factors determining kaolin properties.
Black sand has become the necessary mineral material for dozens of industries such as paper, ceramics, rubber, chemical industry, coatings, medicine and national defense.