Editing Borate (section)

=== Complex oxyanions containing boron ===
More complex anions can be formed by condensing borate triangles or tetrahedra with other [[oxyanion]]s to yield materials such as [[borosulfates]], [[boroselenates]], [[borotellurates]], [[boroantimonates]], [[borophosphates]], or [[boroselenites]].

[[Borosilicate|Borosilicate glass]], also known as [[pyrex]], can be viewed as a [[silicate]] in which some [SiO<sub>4</sub>]<sup>4−</sup> units are replaced by [BO<sub>4</sub>]<sup>5−</sup> centers, together with additional cations to compensate for the difference in valence states of Si(IV) and B(III). Because this substitution leads to imperfections, the material is slow to crystallise. It forms a glass with a low [[coefficient of thermal expansion]], thus resistant to cracking when heated, unlike [[soda glass]].