How are soil minerals classified? What are the definitions for dark and light silicates? Give an example for each type of the silicate minerals.

Soil mineral classification:

Native elements

Sulphides

Sulfosales

Oxides and hydroxides

Halides

Carbonates, nitrates and borates

Sulfates and chromates

Volframatos and molibdatos

Phosphates, arseniates and vanadates

Silicates

Explanation:

Native Elements : they are those found in nature in their purest form, they are divided into metallic and non-metallic, and they are connected by the transition class of semimetals.

Sulphides : sulphides are very important since they comprise most mineral ores. This class includes sulfoarseniurs, arsenides and tellurides, which are similar to sulfides but more rare.

Sulfosales : in this group of minerals, sulfur takes the place of oxygen in the most common and best known oxygenated acids, such as carbonic acid, sulfuric acid or phosphoric acid. Sulfosales are important because they can indicate a certain number of sulfur minerals other than sulfides.

Oxides and Hydroxides : in this class are those natural compounds in which oxygen appears combined with one or more metals, whose appearance and characteristics are diverse. Oxides, for example, are a group of relatively hard, dense and refractory minerals; they usually occur accessoryly in igneous and metamorphic rocks, and in the form of dendritic grains resistant to sediments.

Hydroxides tend to be less hard and of lower density, and appear mainly as secondary alloys or as weathering products, such as limonite, from iron compounds, antimonite stibiconite.

Halides: this group of minerals consists of chemical combinations of metals with halogens such as fluorine, chlorine, bromine and iodine. They generally have low hardness, a low specific weight and vitreous brightness; Its color can vary a lot, as in the case of fluorite and some can be considered of great economic importance. Halides are the most perfect examples of the pure ionic bond mechanism

Carbonates, nitrates and borates : are those minerals that are constituted by the chemical combination of a metal with the anionic carbonate group, so these are the most widespread. Among its characteristics it can be mentioned that they have medium or low hardness, they are generally white, but they can also have bright colors, sometimes they are transparent or translucent so they are easily located in beautiful crystallizations

Sulfates and Chromates : the minerals in this group have a hardness of less than 3.5, for example mineral species rich in water, whose hardness drops to 2. Their optical properties highlight the smaller values of the double refractive indexes.

Volframatos (or tungstenatos) and molibdatos : It is a small group of ore minerals that are colorful and interesting. Tungsten (W) has a much greater atomic weight (184) than molybdenum (96), both belong to the same family of the periodic table and, due to lanthanide contraction, have the same ionic radius.

Phosphates, Arsenate and Vanadatos : this class comprises a large number of brightly colored minerals that are little known. They are characterized by the presence, in the anionic group, of phosphorus (phosphates), arsenic (arseniates) and vanadium (vanadates).

Silicates : this classification of silicates, about one third of the known minerals are found. They are important because many are precious as gems and others are industrially exploited. Silicates are the most important ceramic materials.

The solidification of magma produces a great diversity in the mineral compositions that make up the rocks. There are general categories that are adapted to the amounts of light and dark silicates in the rocks.

Dark silicates are also called ferromagnesians, due to the presence of iron and magnesium in them. These include olivine, pyroxene, amphibole and biotite. The light colored silicates are quartz, muscovite and feldspar.