Another typical metamorphic mineral family are the Garnets. They are Nesosilicates, that is they are structured by isolated groups of SiO₄^4- tetrahedrons; in this case the groups are made of 3 tetrahedrons: (SiO₄)₃^5-. Aluminum is often found bonded to those groups to form the typical Garnet radical: Al₂(SiO₄)₃^3-, but ferric iron (III) is also common in Andradite, as chrome is in Uvarovite. This radical may also bond magnesium, iron and calcium.

Mg		Fe		Mn		Fe3+		Al		Cr
Mg3Al2(SiO4)3		Fe3Al2(SiO4)3		Mn3Al2(SiO4)3		Ca3Fe2(SiO4)3		Ca3Al2(SiO4)3		Ca3Cr2(SiO4)3
Pirope		Almandine		Spessartite		Andradite		Grossular		Uvarovite
						<———		Calcic Garnets		———>

Another group of nesosilicates is an important indicator of a metamorphic rock’s formation temperature: the aluminum silicate Al₂SiO₅. It exists in three polymorphs, never to be found together in the same rock, since they are stable at different pressure and temperature conditions: Andalusite forms at low pressure (LP) but variable temperatures; Cyanite only forms at high pressure (HP > 4 Kbar); Syllimanite forms at high temperature (HT) but variable pressure.

HP	LP	HT
Al2SiO5
Cyanite	Andalusite	Syllimanite

In some cases, the tetrahedron groups are formed by Si₂O₇^6- pairs (left) and are called Sorosilicates. In the Epidote group the tetrahedrons are bonded to calcium, ferric iron and aluminum, and also to a SiO₄ group. Most common Epidotes are the Zoisite (orthorombic) and the Clinozoisite (monocline):

Fe3+		Al
Ca2(Al,Fe)3O(SiO4)(Si2O7)(OH)		Ca2Al3O(SiO4)(Si2O7)(OH)
Epidote		Zoisite