Garnet - Feldspathoid

Garnet (Group and Supergroup)

General Formula: $\text{X}_3\text{Z}_2(\text{SiO}_4)_3$

• X (Divalent site): Mg, Ca, $\text{Fe}^{2+}$, $\text{Mn}^{2+}$, etc.


• Z (Trivalent site): Al, $\text{Fe}^{3+}$, $\text{Cr}^{3+}$, $\text{V}^{3+}$, etc.


• Substitution: Trace amounts of Sn may substitute for $\text{Fe}^{3+}$.

Taxonomy: Garnet Supergroup.

Etymology and Historical Nomenclature:

• Classical Greek: The mineral was likely first described by Tyrtamus—commonly known by his honorific, Theophrastus—circa 325–300 BC, under the name Anthrax (Ανθραξ). However, this term was also applied to ruby and pinkish-red sapphire.


• Roman Period: In 77–79 AD, Pliny the Elder referred to the mineral as Carchedonius Garamanticus (Carthaginian or Garamantic Carbuncle).


• Linguistic Origin: The modern name is derived from the Latin granatum (“pomegranate”), due to the visual resemblance of the crystals to the seeds of the fruit.

Classification Note:

“Garnet” functions as the classical name for a group of silicate minerals sharing an isostructural framework. It should not be confused with the Garnet Supergroup, which is a broader taxonomic classification that also encompasses garnet-type vanadates and other related species.