garnet An important rock-forming mineral group, with the general formula X₃Y₂Si₃O₁₂, where X may be Ca, Mg, Fe²⁺, or Mn and Y may be Al, Fe³⁺, or Cr³⁺; the main minerals are grossular (X =Mg, Y = Al), pyrope (X = Mg, Y = Al), almandine (X = Fe²⁺, Y = Al), spessartine (X=Mn, Y=Al), andradite (X = Ca, Y = Fe³⁺), and uvarovite (X = Ca, Y = Cr³⁺), and there is continuous chemical variation in the group; an unusual variety called hydrogrossular Ca₃Al₂[SiO₄]₂[SiO₄]_{1 − m} (OH)_4m has hydroxyl ions in the structure and is found in the rare rock type rodingite; sp. gr. 3.6–4.3; hardness 7.0–7.5; colour very variable depending on its chemical composition, and can vary from shades of deep red-brown to almost black, green, white, yellow, and brown; usually vitreous lustre; crystals cubic, with the most common form being dodecahedra; no cleavage; found in high-grade metamorphic and igneous rocks, in beach sands, and alluvial placers. Transparent pyrope crystals may be used as gemstones, but garnet is more generally used as an abrasive.

gar·net / ˈgärnit/ • n. a precious stone consisting of a deep red vitreous silicate mineral. ∎ Mineralogy any of a class of silicate minerals including this, which belong to the cubic system and have the general chemical formula A₃B₂(SiO₄)₃ (A and B being respectively divalent and trivalent metals).

garnet vitreous mineral, a precious kind of which is used as a gem. XIII. ME. gernet, grenat, prob. — MDu. gernate, garnate — OF. grenat — medL. grānātus, perh. transf. use of L. grānātum POMEGRANATE, the stone being compared in colour to the pulp of the fruit.

garnet Two series of orthosilicate minerals found in metamorphic rocks and pegmatites. Some varieties are important as gemstones. Hardness 6.5–7.5; r.d. 4.

Garnet

Gemstone that was popularly believed to preserve health and promote joy, but in the case of lovers might cause discord.