Content:
The most important ones are Ca2+, Mg2+, K+, Na+, Ba2+, Sr2+, Pb2+, Fe3+, Al3+, Cu2+. There are more than 170 kinds of known sulfate minerals. Although they only account for 0.1% of the total weight of the earth's crust, the gypsum, anhydrite, barite, and thenardite in them can be enriched into deposits of industrial significance. Most of the sulfate minerals are salts with relatively complex compositions, so the crystal structure with a low degree of symmetry is mainly monoclinic and orthorhombic. And because most sulfate minerals contain water, its most prominent physical property is low hardness, generally between 2-3.5. In addition, the color is generally colorless and white, and the specific gravity is generally not large, between 2-4. The formation of sulfate minerals requires high oxygen concentration and low temperature conditions, so the surface part is the most suitable place for the formation of sulfate minerals. In this type of minerals, the external cause is far more important than the internal cause. Among them, sulfate minerals formed by oxidation of primary metal sulfides account for almost half of this type of minerals. The chemically deposited sulfate minerals in the ocean basins are mainly hydrous sulfates of potassium, sodium, calcium, magnesium, barium, and aluminum. As for the sulfate minerals of endogenous hydrothermal origin, they are mainly anhydrous sulfates such as barium, calcium, strontium, and aluminum, which are found in mid-low temperature hydrothermal veins or as products of low-temperature hydrothermal wall rock alteration.
Cause:
Volcanic eruptions will emit sulfur, and sulfur will burn to produce sulfur dioxide. When sulfur dioxide encounters water vapor, sulfurous acid is formed. The sulfurous acid is oxidized by oxygen in the air to sulfuric acid. The sulfuric acid reacts with metal oxides in the earth's crust to form sulfates.