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The basic level of definition is that of mineral species, each of which is distinguished from the others by unique chemical and physical properties. For example, quartz is defined by its formula , SiO 2 , and a specific crystalline structure that distinguishes it from other minerals with the same chemical formula (termed polymorphs ).
Likewise, if a substance can form crystals, it can also form polycrystals. For pure chemical elements, polymorphism is known as allotropy. For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have very different properties.
The atoms are linked in a continuous framework of SiO 4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO 2. Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral.
A rock may consist of one type of mineral or may be an aggregate of two or more different types of minerals, spacially segregated into distinct phases. Some natural solid substances without a definite crystalline structure, such as opal or obsidian, are more properly called mineraloids. If a chemical compound occurs naturally with different ...
The proportion of silica in rocks and minerals is a major factor in determining their names and properties. [7] Rock outcrop along a mountain creek near Orosí, Costa Rica. Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size.
The two allotropes that are encountered at normal pressure and temperature, α-tin and β-tin, are more commonly known as gray tin and white tin respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C and pressures above several GPa. [23] White tin is metallic, and is the stable crystalline form at or above room ...
Mineralogy applies principles of chemistry, geology, physics and materials science to the study of minerals. Mineralogy [n 1] is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy ...
When treated with calcium oxides and water, silicate minerals form Portland cement. Equilibria involving hydrolysis of silicate minerals are difficult to study. The chief challenge is the very low solubility of SiO 4 4- and its various protonated forms.