Disilikaatit

Disilikaatit are a class of silicate minerals characterized by the presence of the discrete [Si2O7]6- anion. This anion consists of two silicon atoms bonded to each other via an oxygen atom, with each silicon atom also bonded to three other oxygen atoms. This arrangement results in a structure where two SiO4 tetrahedra share a single oxygen atom. Disilicate minerals are a subset of the sorosilicates, which are silicates containing pairs of SiO4 tetrahedra.

Common examples of disilicate minerals include:

* **Hemimorphite:** A zinc silicate mineral often found in oxidized zinc deposits. It exhibits a distinct hemimorphic crystal habit, meaning it has different structures at opposite ends of a crystallographic axis.

* **Epidote:** A group of common rock-forming minerals found in metamorphic rocks and some igneous rocks. They are known for their characteristic green color and are often used as gemstones.

* **Axinite:** A group of borosilicate minerals that typically occur in metamorphic rocks. They are characterized by their distinctive wedge-shaped crystals and often display striking pleochroism.

* **Melilite:** A group of minerals found in mafic and ultramafic igneous rocks, as well as in some impactites. They have a general formula of (Ca,Na)2(Mg,Fe2+,Al)(Si,Al)2O7.

The physical properties of disilicate minerals vary depending on their specific chemical composition and crystal structure. They are generally hard and relatively dense. Their occurrence is widespread in various geological environments, particularly in metamorphic and igneous settings. The [Si2O7]6- anion imparts specific structural and chemical characteristics to these minerals, influencing their stability and reactivity.